fuse_session_mount() may print errors to stderr, if we daemonize before
that than these are lost.

The filesystem daemon is responsible for implementing eg. st_atime updates, so passing
options like relatime to the kernel results in them being silently ignored. Instead, such
options need to be interpreted (and filtered out) by the filesystem daemon.

Added a secondary check in fuse_lib_unlink() after hide_node()
to check again under a lock if the (now hidden) file is still open.
If not then delete it.

This should synchronise fuse_lib_unlink() with fuse_lib_release(),
when nullpath_ok is set.

Previously, in the high level API if we received a signal between
setting up signal handlers and processing INIT, we would leak

```
$ ./example/hello -s -d -f mountpoint/
[9/9] Linking target example/hello_ll
FUSE library version: 3.14.1
nullpath_ok: 0

=================================================================
==178330==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 352 byte(s) in 1 object(s) allocated from:
    #0 0x7fbb19abf411 in __interceptor_calloc /usr/src/debug/gcc/gcc/libsanitizer/asan/asan_malloc_linux.cpp:77
    #1 0x7fbb1a0efd3b in fuse_fs_new ../lib/fuse.c:4814
    #2 0x7fbb1a0f02b5 in fuse_new_31 ../lib/fuse.c:4913
    #3 0x7fbb1a10ec5e in fuse_main_real ../lib/helper.c:345
    #4 0x5625db8ab418 in main ../example/hello.c:176
    #5 0x7fbb1983c78f  (/usr/lib/libc.so.6+0x2378f)

SUMMARY: AddressSanitizer: 352 byte(s) leaked in 1 allocation(s).
```

That's because `fuse_lowlevel.c`s `fuse_session_destroy` would only call
the user supplied `op.destroy`, if INIT had been processed, but the high
level API relied on `op.destroy` to free `f->fs`.

This patch moves the freeing into `fuse_destroy` that will always be
called by our high-level API.

Before:

```
$ doxygen doc/Doxyfile
warning: Tag 'COLS_IN_ALPHA_INDEX' at line 707 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Tag 'PERL_PATH' at line 1048 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Tag 'CLASS_DIAGRAMS' at line 1061 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Tag 'MSCGEN_PATH' at line 1070 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Tag 'DOT_TRANSPARENT' at line 1207 of file 'doc/Doxyfile' has become obsolete.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
warning: Changing CLASS_GRAPH option to TEXT because obsolete option CLASS_DIAGRAM was found and set to NO.
/Users/matthias/prog/fuser/libfuse/include/fuse.h:934: warning: argument 'private_data' of command @param is not found in the argument list of fuse_new_31(struct fuse_args *args, const struct fuse_operations *op, size_t op_size, void *user_data)
/Users/matthias/prog/fuser/libfuse/include/fuse.h:934: warning: The following parameter of fuse_new_31(struct fuse_args *args, const struct fuse_operations *op, size_t op_size, void *user_data) is not documented:
  parameter 'user_data'
```

So let's try `doxygen -u doc/Doxyfile`.  After:

```
$ doxygen doc/Doxyfile
/Users/matthias/prog/fuser/libfuse/include/fuse.h:934: warning: argument 'private_data' of command @param is not found in the argument list of fuse_new_31(struct fuse_args *args, const struct fuse_operations *op, size_t op_size, void *user_data)
/Users/matthias/prog/fuser/libfuse/include/fuse.h:934: warning: The following parameter of fuse_new_31(struct fuse_args *args, const struct fuse_operations *op, size_t op_size, void *user_data) is not documented:
  parameter 'user_data'
```

The generated documentation `doc/html` does not differ.

For ease of review, here's a diff with all blank lines and comments removed via `grep -vE '^#|^$' doc/Doxyfile`

```
diff --git a/doc/Doxyfile.old b/doc/Doxyfile.new
index dbf469b..3f56d32 100644
--- a/doc/Doxyfile.old
+++ b/doc/Doxyfile.new
@@ -3,0 +4,2 @@ PROJECT_NUMBER         =
+PROJECT_BRIEF          =
+PROJECT_LOGO           =
@@ -5,0 +8,2 @@ CREATE_SUBDIRS         = NO
+CREATE_SUBDIRS_LEVEL   = 8
+ALLOW_UNICODE_NAMES    = NO
@@ -26,0 +31 @@ JAVADOC_AUTOBRIEF      = NO
+JAVADOC_BANNER         = NO
@@ -28,0 +34 @@ MULTILINE_CPP_IS_BRIEF = NO
+PYTHON_DOCSTRING       = YES
@@ -36,0 +43,5 @@ OPTIMIZE_OUTPUT_VHDL   = NO
+OPTIMIZE_OUTPUT_SLICE  = NO
+EXTENSION_MAPPING      =
+MARKDOWN_SUPPORT       = YES
+TOC_INCLUDE_HEADINGS   = 5
+AUTOLINK_SUPPORT       = YES
@@ -41,0 +53 @@ DISTRIBUTE_GROUP_DOC   = NO
+GROUP_NESTED_COMPOUNDS = NO
@@ -42,0 +55,2 @@ SUBGROUPING            = YES
+INLINE_GROUPED_CLASSES = NO
+INLINE_SIMPLE_STRUCTS  = NO
@@ -43,0 +58,2 @@ TYPEDEF_HIDES_STRUCT   = NO
+LOOKUP_CACHE_SIZE      = 0
+NUM_PROC_THREADS       = 1
@@ -45,0 +62,2 @@ EXTRACT_PRIVATE        = NO
+EXTRACT_PRIV_VIRTUAL   = NO
+EXTRACT_PACKAGE        = NO
@@ -49,0 +68 @@ EXTRACT_ANON_NSPACES   = NO
+RESOLVE_UNNAMED_PARAMS = YES
@@ -56,0 +76,2 @@ HIDE_SCOPE_NAMES       = NO
+HIDE_COMPOUND_REFERENCE= NO
+SHOW_HEADERFILE        = YES
@@ -57,0 +79,2 @@ SHOW_INCLUDE_FILES     = YES
+SHOW_GROUPED_MEMB_INC  = NO
+FORCE_LOCAL_INCLUDES   = NO
@@ -60,0 +84 @@ SORT_BRIEF_DOCS        = NO
+SORT_MEMBERS_CTORS_1ST = NO
@@ -62,0 +87 @@ SORT_BY_SCOPE_NAME     = NO
+STRICT_PROTO_MATCHING  = NO
@@ -72,0 +98,2 @@ FILE_VERSION_FILTER    =
+LAYOUT_FILE            =
+CITE_BIB_FILES         =
@@ -76,0 +104 @@ WARN_IF_DOC_ERROR      = YES
+WARN_IF_INCOMPLETE_DOC = YES
@@ -77,0 +106,2 @@ WARN_NO_PARAMDOC       = NO
+WARN_IF_UNDOC_ENUM_VAL = NO
+WARN_AS_ERROR          = NO
@@ -78,0 +109 @@ WARN_FORMAT            = "$file:$line: $text"
+WARN_LINE_FORMAT       = "at line $line of file $file"
@@ -82 +113,5 @@ INPUT_ENCODING         = UTF-8
-FILE_PATTERNS          = *.h *.c *.h *.dox
+INPUT_FILE_ENCODING    =
+FILE_PATTERNS          = *.h \
+                         *.c \
+                         *.h \
+                         *.dox
@@ -89 +124,2 @@ EXAMPLE_PATH           = example
-EXAMPLE_PATTERNS       = *.c *.h
+EXAMPLE_PATTERNS       = *.c \
+                         *.h
@@ -94,0 +131,3 @@ FILTER_SOURCE_FILES    = NO
+FILTER_SOURCE_PATTERNS =
+USE_MDFILE_AS_MAINPAGE =
+FORTRAN_COMMENT_AFTER  = 72
@@ -100,0 +140 @@ REFERENCES_LINK_SOURCE = YES
+SOURCE_TOOLTIPS        = YES
@@ -104 +143,0 @@ ALPHABETICAL_INDEX     = NO
-COLS_IN_ALPHA_INDEX    = 5
@@ -112 +151,10 @@ HTML_STYLESHEET        =
-GENERATE_HTMLHELP      = NO
+HTML_EXTRA_STYLESHEET  =
+HTML_EXTRA_FILES       = doc/fast17-vangoor.pdf
+HTML_COLORSTYLE        = AUTO_LIGHT
+HTML_COLORSTYLE_HUE    = 220
+HTML_COLORSTYLE_SAT    = 100
+HTML_COLORSTYLE_GAMMA  = 80
+HTML_TIMESTAMP         = NO
+HTML_DYNAMIC_MENUS     = YES
+HTML_DYNAMIC_SECTIONS  = YES
+HTML_INDEX_NUM_ENTRIES = 100
@@ -114,0 +163 @@ DOCSET_FEEDNAME        = "Doxygen generated docs"
+DOCSET_FEEDURL         =
@@ -116,2 +165,3 @@ DOCSET_BUNDLE_ID       = org.doxygen.Project
-HTML_DYNAMIC_SECTIONS  = YES
-HTML_EXTRA_FILES = doc/fast17-vangoor.pdf
+DOCSET_PUBLISHER_ID    = org.doxygen.Publisher
+DOCSET_PUBLISHER_NAME  = Publisher
+GENERATE_HTMLHELP      = NO
@@ -123,0 +174,10 @@ TOC_EXPAND             = NO
+GENERATE_QHP           = NO
+QCH_FILE               =
+QHP_NAMESPACE          = org.doxygen.Project
+QHP_VIRTUAL_FOLDER     = doc
+QHP_CUST_FILTER_NAME   =
+QHP_CUST_FILTER_ATTRS  =
+QHP_SECT_FILTER_ATTRS  =
+QHG_LOCATION           =
+GENERATE_ECLIPSEHELP   = NO
+ECLIPSE_DOC_ID         = org.doxygen.Project
@@ -125 +184,0 @@ DISABLE_INDEX          = NO
-ENUM_VALUES_PER_LINE   = 4
@@ -126,0 +186,2 @@ GENERATE_TREEVIEW      = NO
+FULL_SIDEBAR           = NO
+ENUM_VALUES_PER_LINE   = 4
@@ -127,0 +189,3 @@ TREEVIEW_WIDTH         = 250
+EXT_LINKS_IN_WINDOW    = NO
+OBFUSCATE_EMAILS       = YES
+HTML_FORMULA_FORMAT    = png
@@ -128,0 +193,14 @@ FORMULA_FONTSIZE       = 10
+FORMULA_MACROFILE      =
+USE_MATHJAX            = NO
+MATHJAX_VERSION        = MathJax_2
+MATHJAX_FORMAT         = HTML-CSS
+MATHJAX_RELPATH        =
+MATHJAX_EXTENSIONS     =
+MATHJAX_CODEFILE       =
+SEARCHENGINE           = NO
+SERVER_BASED_SEARCH    = NO
+EXTERNAL_SEARCH        = NO
+SEARCHENGINE_URL       =
+SEARCHDATA_FILE        = searchdata.xml
+EXTERNAL_SEARCH_ID     =
+EXTRA_SEARCH_MAPPINGS  =
@@ -129,0 +208,18 @@ GENERATE_LATEX         = NO
+LATEX_OUTPUT           = latex
+LATEX_CMD_NAME         =
+MAKEINDEX_CMD_NAME     = makeindex
+LATEX_MAKEINDEX_CMD    = makeindex
+COMPACT_LATEX          = NO
+PAPER_TYPE             = a4
+EXTRA_PACKAGES         =
+LATEX_HEADER           =
+LATEX_FOOTER           =
+LATEX_EXTRA_STYLESHEET =
+LATEX_EXTRA_FILES      =
+PDF_HYPERLINKS         = YES
+USE_PDFLATEX           = YES
+LATEX_BATCHMODE        = NO
+LATEX_HIDE_INDICES     = NO
+LATEX_BIB_STYLE        = plain
+LATEX_TIMESTAMP        = NO
+LATEX_EMOJI_DIRECTORY  =
@@ -130,0 +227,5 @@ GENERATE_RTF           = NO
+RTF_OUTPUT             = rtf
+COMPACT_RTF            = NO
+RTF_HYPERLINKS         = NO
+RTF_STYLESHEET_FILE    =
+RTF_EXTENSIONS_FILE    =
@@ -131,0 +233,4 @@ GENERATE_MAN           = NO
+MAN_OUTPUT             = man
+MAN_EXTENSION          = .3
+MAN_SUBDIR             =
+MAN_LINKS              = NO
@@ -132,0 +238,5 @@ GENERATE_XML           = NO
+XML_OUTPUT             = xml
+XML_PROGRAMLISTING     = YES
+XML_NS_MEMB_FILE_SCOPE = NO
+GENERATE_DOCBOOK       = NO
+DOCBOOK_OUTPUT         = docbook
@@ -134,0 +245,3 @@ GENERATE_PERLMOD       = NO
+PERLMOD_LATEX          = NO
+PERLMOD_PRETTY         = YES
+PERLMOD_MAKEVAR_PREFIX =
@@ -148,3 +261,2 @@ EXTERNAL_GROUPS        = YES
-PERL_PATH              = /usr/bin/perl
-CLASS_DIAGRAMS         = NO
-MSCGEN_PATH            =
+EXTERNAL_PAGES         = YES
+DIA_PATH               =
@@ -152,0 +265,4 @@ HAVE_DOT               = NO
+DOT_NUM_THREADS        = 0
+DOT_COMMON_ATTR        = "fontname=Helvetica,fontsize=10"
+DOT_EDGE_ATTR          = "labelfontname=Helvetica,labelfontsize=10"
+DOT_NODE_ATTR          = "shape=box,height=0.2,width=0.4"
@@ -154 +270 @@ DOT_FONTPATH           =
-CLASS_GRAPH            = YES
+CLASS_GRAPH            = TEXT
@@ -157,0 +274,3 @@ UML_LOOK               = NO
+UML_LIMIT_NUM_FIELDS   = 10
+DOT_UML_DETAILS        = NO
+DOT_WRAP_THRESHOLD     = 17
@@ -164,0 +284 @@ DIRECTORY_GRAPH        = YES
+DIR_GRAPH_MAX_DEPTH    = 1
@@ -165,0 +286 @@ DOT_IMAGE_FORMAT       = png
+INTERACTIVE_SVG        = NO
@@ -167,0 +289,5 @@ DOTFILE_DIRS           =
+MSCFILE_DIRS           =
+DIAFILE_DIRS           =
+PLANTUML_JAR_PATH      =
+PLANTUML_CFG_FILE      =
+PLANTUML_INCLUDE_PATH  =
@@ -170 +295,0 @@ MAX_DOT_GRAPH_DEPTH    = 1000
-DOT_TRANSPARENT        = NO
@@ -174 +298,0 @@ DOT_CLEANUP            = YES
-SEARCHENGINE           = NO
```

* Fuse mount: make auto_unmount compatible with suid/dev mount options

> When you run as root, fuse normally does not call fusermount but uses
> the mount system call directly. When you specify auto_unmount, it goes
> through fusermount instead. However, fusermount is a setuid binary that
> is normally called by regular users, so it cannot in general accept suid
> or dev options.

In this patch, we split up how fuse mounts as root when `auto_unmount`
is specified.

First, we mount using system calls directly, then we reach out to
fusermount to set up auto_unmount only (with no actual mounting done in
fusermount).

Fixes: #148 

This syncs fuse_kernel.h to <linux-6.3>/include/uapi/linux/fuse.h

Special handling is done for setxattr as in linux commit
52a4c95f4d24b struct fuse_setxattr_in was extended. Extended
struct is only used when FUSE_SETXATTR_EXT is passed in FUSE_INIT
reply.

Before:

```
=============================== warnings summary ===============================
test/test_ctests.py:12
  /tmp/libfuse-build-mB50ZC/build-gcc-9/test/test_ctests.py:12: DeprecationWarning: The distutils package is deprecated and slated for removal in Python 3.12. Use setuptools or check PEP 632 for potential alternatives
    from distutils.version import LooseVersion

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
```