manual: Update prototypes for alphasort and friends

The four functions {alpha,version}sort{,64} take parameters of type
const struct dirent{,64} **, not const void *.

Signed-off-by: Rasmus Villemoes <rv@rasmusvillemoes.dk>
Fix log10 (1) in round-downward mode (bug 16977).

As with various other issues of this kind, bug 16977 is log10 (1)
wrongly returning -0 rather than +0 in round-downward mode because of
an implementation effectively in terms of log1p (x - 1).  This patch
fixes the issue in the same way used for log.

Tested x86_64 and x86 and ulps updated accordingly.  Also tested for
mips64 to confirm a fix was needed for ldbl-128 and to validate that
fix (also applied to ldbl-128ibm since that version of logl is
essentially the same as the ldbl-128 one).

	[BZ #16977]
	* sysdeps/i386/fpu/e_log10.S (__ieee754_log10): Take absolute
	value when x - 1 is zero.
	* sysdeps/i386/fpu/e_log10f.S (__ieee754_log10f): Likewise.
	* sysdeps/i386/fpu/e_log10l.S (__ieee754_log10l): Likewise.
	* sysdeps/ieee754/ldbl-128/e_log10l.c (__ieee754_log10l): Return
	0.0L for an argument of 1.0L.
	* sysdeps/ieee754/ldbl-128ibm/e_log10l.c (__ieee754_log10l):
	Likewise.
	* sysdeps/x86_64/fpu/e_log10l.S (__ieee754_log10l): Take absolute
	value when x - 1 is zero.
	* math/libm-test.inc (log10_test): Use ALL_RM_TEST.
	* sysdeps/i386/fpu/libm-test-ulps: Update.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
alpha: Remove nptl/fork.c

The merge at ab21431318d99c94e644606dee1e6a4545d98007 failed
to properly remove the file.
alpha: Merge standard and nptl clone.S
alpha: Consolidate NPTL/non versions of vfork
alpha: Move remaining files out of sysdeps/unix/sysv/linux/alpha/nptl/
Define TSVTX in tar.h for older POSIX (bug 16978).

As noted in bug 16978, older POSIX versions include

in the specified contents of <tar.h>, with only the 2001 edition
introducing the notion of XSI-conditional definitions and conditioning
that definition.  Thus, this macro should be defined for
!__USE_XOPEN2K as well as for __USE_XOPEN, and this patch duly defines
it in that case.  Tested x86_64.

	[BZ #16978]
	* posix/tar.h [!__USE_XOPEN2K] (TSVTX): Define macro.
	* conform/Makefile (test-xfail-POSIX/tar.h/conform): Remove
	variable.