* src/sendfile.c (sys_sendfile): Expose this function on GNU/Hurd,
  which provides the same interface as Linux.

Reviewed by Fergus Henderson.

(typically the only change is in the FSF street address).  Add Google
copyright line in some places it was missing.  Add GPLv2 notice to
avahi patches.

OKed by fergus

Also, fix the emacs var-setting line: it was missing a semicolon
before, which means the entire line was being ignored.

No contentful change.

Reviewed by fergus@google.com

lines.  Fixed up resulting mis-indented code I noticed (mostly in
files that used 8 space indents, or used 4-space and 8-space indents
in the same file (!)).  Added the emacs tab-var setting for all files,
not just some of them.

I also added in copyright notices for files I noticed that didn't have
them.  We'll want to do another pass-through to fix these up properly,
though.

I used the following perl snippet to check for mis-indented code after
converting tabs to whitespace:

  $ for i in *.{c,h}; do echo $i; perl -nle 'if ($indent > 0) {$sp=" " x $indent; /^$sp[^ ]/ && print "$.: $_"; $indent=0;}; if (/^( *).*{/ ) {$indent=length($1);} else {$indent=0;}' $i; done | less

It had false positives, but hopefully didn't miss anything.

Reviewed by klarlund@google.com

affects the way emacs users will see these files, when visiting them
in emacs.  In particular, tabs will show up as 4 spaces, which is
(clearly) the setting the original distcc author used when writing the
code.

We also set an emacs variable to never insert new tabs, but use spaces
instead.  This will help stop the problem we have now with mixed tabs
and spaces.  In a future cleanup, we may replace all tabs with 4
spaces, and make other whitespace improvements.

The final new variable set, is to set line-wrapping at 78 chars.
Personally, I would have made it more like 72, but some existing files
already had the 78 limit, so I just do that everywhere, to be
consistent.

Reviewed by fergus@google.com

safe to fall back on readwrite(), do that.  Before we only did this
for certain errors, but we might as well do it for any error we don't
expect to be able to recover from.

Tested by running on mac os x 10.4, which has a problem with sendfile
failing sometimes.  The relevant test succeeds after this patch.

Reviewed by fergus@google.com

(1) Correct order of -Is in Makefile.

(2) remove unnessary PATH modification in configure.ac (this is fergus's
suggestion -- hopefully this will do, this replaces a circumvention mechanism I
had originally concocted.

(3) Fix place of the include of popt in CPPFLAGS.

(4) Convert quoted includes of config.h to angle bracket includes so that the
build version, not the source version, of this file is picked up.

The order of -Is in the build system is wrong: it contradicts the
VPATH mechanism.  

This means that builds in a build directory different from that
of the source (distribution) directory will find wrong files even
after the hapless developer has issued only a 'configure' command
in the source directory (but not actually 'made' any thing
there).  For in that case, the src/config.h will be generated in
the source directory and this will be the file picked in the
build directory even if that directory has it's own src/config.h.
This can lead to wrong builds and it can be hard to diagnose the
problem.

Currently, this what CPPFLAGS end up being (as found in the
generated Makefile):

  CPPFLAGS =  -DHAVE_CONFIG_H -D_GNU_SOURCE \
              -I../distcc/popt -I../distcc/src \
              ${DIR_DEFS} \
              -Isrc -Ilzo \
              -I"$(srcdir)/src" -I"$(srcdir)/lzo" \

Here my source dir was ../distcc.  

The presence of '-I../distcc/popt' in front of -Isrc is the exact
opposite of the semantics of VPATH mechanism, which looks for
files in the build directory, then in the source directory.  

Also, note the remarks in:

  http://www.gnu.org/software/autoconf/manual/autoconf.html#Configuration-Headers

(they do not quite correctly discuss the search path, btw).

TESTING: I verified that with a corrupted config.h file in the source directory,
building now succeeds.

Also: make distcheck (it fails the same place as before: this is corrected in
another change of mine --- I'll verify that with that change in place, this
change makes 'make distcheck' succeed.)

REVIEWERS: fergus@google.com, csilvers@google.com

ENONSYS and EINVAL errors: fall back to using read() and write().
This fixes the failure of SyntaxError_Case and MissingCompiler_Case
on FreeBSD.

Tested by "make check".

Reviewers: Craig Silverstein

Looking at the man pages, it looks like os x sendfile is pretty much
the same as BSD's, so I copied much of the code from the existing BSD
case.

Tested by ensuring the code compiles and links on os x 10.5.  No
attempt to see if it runs correctly, though.

Reviewed by fergus@google.com