Add <bits/indirect-return.h> and include it in <ucontext.h>.
__INDIRECT_RETURN defined in <bits/indirect-return.h> indicates if
swapcontext requires special compiler treatment.  The default
__INDIRECT_RETURN is empty.

On x86, when shadow stack is enabled, __INDIRECT_RETURN is defined
with indirect_return attribute, which has been added to GCC 9, to
indicate that swapcontext returns via indirect branch.  Otherwise
__INDIRECT_RETURN is defined with returns_twice attribute.

When shadow stack is enabled, remove always_inline attribute from
prepare_test_buffer in string/tst-xbzero-opt.c to avoid:

tst-xbzero-opt.c: In function ‘prepare_test_buffer’:
tst-xbzero-opt.c:105:1: error: function ‘prepare_test_buffer’ can never be inlined because it uses setjmp
 prepare_test_buffer (unsigned char *buf)

when indirect_return attribute isn't available.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

	* bits/indirect-return.h: New file.
	* misc/sys/cdefs.h (__glibc_has_attribute): New.
	* sysdeps/x86/bits/indirect-return.h: Likewise.
	* stdlib/Makefile (headers): Add bits/indirect-return.h.
	* stdlib/ucontext.h: Include <bits/indirect-return.h>.
	(swapcontext): Add __INDIRECT_RETURN.
	* string/tst-xbzero-opt.c (ALWAYS_INLINE): New.
	(prepare_test_buffer): Use it.

	* bits/shm.h (struct shmid_ds): Make shm_segsz field size_t instead of
	int.
	* sysdeps/gnu/bits/shm.h (struct shmid_ds): Likewise.

When compiling C++ code with -mabi=ieeelongdouble, KCtype is
unavailable and the long double type should be used instead.

This is also providing macro __HAVE_FLOAT128_UNLIKE_LDBL in order to
identify the kind of long double type is being used in the current
compilation unit.
Notice that bits/floatn.h cannot benefit from the new macro due to order
of header inclusion.

	* bits/floatn-common.h: Define __HAVE_FLOAT128_UNLIKE_LDBL.
	* math/math.h: Restrict the prototype definition for the functions
	issignaling(_Float128) and iszero(_Float128); and template
	__iseqsig_type<_Float128>, from __HAVE_DISTINCT_FLOAT128 to
	__HAVE_FLOAT128_UNLIKE_LDBL.
	* sysdeps/powerpc/bits/floatn.h [__HAVE_FLOAT128
	&& (!__GNUC_PREREQ (7, 0) || defined __cplusplus)
	&& __LDBL_MANT_DIG__ == 113]: Use long double suffix for
	__f128() constants; define the type _Float128 as long double;
	and reuse long double in __CFLOAT128.

Signed-off-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>

As for sysctl, ustat has been deprecated in favor of {f}statfs.  Also
some newer ports which uses generic interface builds a stub version that
returns ENOSYS.

This patch deprecates ustat interface by removing ustat.h related headers,
adding a compatibility symbol, and avoiding new ports to build and provide
the symbol.

Checked on x86_64-linux-gnu and i686-linux-gnu.  Also checked with a
check-abi on all affected ABIs.

	* NEWS: Add ustat.h deprecation entry.
	* bits/ustat.h: Remove file.
	* misc/sys/ustat.h: Likewise.
	* misc/ustat.h: Likewise.
	* sysdeps/unix/sysv/linux/generic/ustat.c: Likewise.
	* misc/Makefile (headers): Remove ustat.h and sys/ustat.h.
	* misc/ustat.c (__ustat): Rename to __old_ustat and export only in
	compatibility mode.
	* sysdeps/unix/sysv/linux/ustat.c (__ustat): Likewise.
	* sysdeps/unix/sysv/linux/mips/ustat.c: Define DEV_TO_KDEV and use
	generic Linux implementation.

	* bits/resource.h (RLIM_SAVED_MAX, RLIM_SAVED_CUR): New macros.

	* bits/termios.h [__USE_XOPEN || __USE_XOPEN2K8] (IXANY): Define.
	[__USE_XOPEN && !__USE_XOPEN2K] (IUCLC, OLCUC): Define.
	[__USE_XOPEN] (OFDEL): New macro.
	[__USE_XOPEN && !__USE_XOPEN2K] (XCASE): New macro.

	* bits/types/siginfo_t.h: Remove siginfo struct name, unused and
	non-compliant.

	* bits/sched.h: Include <bits/types/struct_sched_param.h> and move struct
	sched_param definition to it.
	* sysdeps/unix/sysv/linux/bits/sched.h: Likewise.
	* bits/types/struct_sched_param.h: New file.
	* sysdeps/htl/bits/types/struct___pthread_attr.h: Include
	<bits/types/struct_sched_param.h> instead of <sched.h>.
	* posix/Makefile (headers): Add bits/types/struct_sched_param.h.

	* bits/in.h [!__USE_MISC]: Do not define struct ip_opts.
	* conform/data/netinet/in.h-data: Allow sin_ and sin6_ prefix.
	* sysdeps/gnu/bits/msq.h (struct msqid_ds): Use __wait_queue struct
	instead of wait_queue.
	* sysdeps/gnu/bits/shm.h (struct shmid_ds): Use __vm_area_struct
	instead of vm_area_struct.

This reverts commit 783c4820303fb6b031d401564f8089ecaf154b62 which
accidentaly flew out.