Fix build of C mempcpy and stpcpy.

This patch fixes the build of C mempcpy and stpcpy by disabling the
redirection to __mempcpy and __stpcpy asm names if
NO_MEMPCPY_STPCPY_REDIRECT is defined, and defining that macro in the
relevant source files.

Tested for powerpc32 that the build is fixed.

	* include/string.h [NO_MEMPCPY_STPCPY_REDIRECT] (mempcpy): Do not
	redeclare with asm name.
	[NO_MEMPCPY_STPCPY_REDIRECT] (stpcpy): Likewise.
	* string/mempcpy.c (NO_MEMPCPY_STPCPY_REDIRECT): Define before
	including <string.h>.
	* string/stpcpy.c (NO_MEMPCPY_STPCPY_REDIRECT): Likewise.
	* sysdeps/powerpc/powerpc32/power4/multiarch/mempcpy.c
	[!NOT_IN_libc] (NO_MEMPCPY_STPCPY_REDIRECT): Likewise.
	* sysdeps/powerpc/powerpc64/multiarch/mempcpy.c
	[!NOT_IN_libc] (NO_MEMPCPY_STPCPY_REDIRECT): Likewise.
	* sysdeps/powerpc/powerpc64/multiarch/stpcpy.c
	[SHARED && !NOT_IN_libc] (NO_MEMPCPY_STPCPY_REDIRECT): Likewise.
Require GCC 4.6 or later to build glibc.

As discussed in the thread starting at
<https://sourceware.org/ml/libc-alpha/2014-10/msg00792.html>, and
continuing into November, this patch increases the minimum GCC version
for building glibc to 4.6 (there seemed to be no clear consensus for
4.7).  In particular, this allows us to use #pragma GCC diagnostic for
fine-grained warning control with -Werror (subject to establishing a
suitable policy for that use).  The documentation has a statement, as
requested, about the most recent GCC version tested for building
glibc, and I've updated <https://sourceware.org/glibc/wiki/Release> to
refer to updating that statement.  A NEWS entry is added for this
change, although previous such changes didn't get them.

Tested for x86_64 (testsuite, and that installed shared libraries are
unchanged by this patch).

	* configure.ac (libc_cv_compiler_ok): Require GCC 4.6 or later.
	* configure: Regenerated.
	* manual/install.texi (Tools for Compilation): Document a
	requirement of GCC 4.6 or later and that GCC 4.9 is the newest
	compiler verified to work.
	* INSTALL: Regenerated.
Fix sparc build.

	* sysdeps/sparc/sparc64/rtld-memcpy.c (NO_MEMPCPY_STPCPY_REDIRECT):
	Define before including <string/memcpy.c> and <string/mempcpy.c>.
Only declare __sigpause in installed signal.h when necessary.

This patch makes the installed signal.h declare __sigpause only when
necessary (when a macro definition of sigpause makes use of
__sigpause), rather than unconditionally.  This fixes false positives
in the linknamespace tests by making it visible to those tests that no
use of ISO C functionality will actually bring in the definition of
__sigpause and so bring in the other symbols defined in the same
object.  There is no bug filed in Bugzilla because this is fixing
false positives rather than any user-visible bug.

Tested for x86_64 (testsuite, and that installed stripped shared
libraries are unchanged by this patch).

	* signal/signal.h (__sigpause): Only declare if [__USE_XOPEN &&
	!__GNUC__].
	* include/signal.h (__sigpause): Move declaration above call to
	libc_hidden_proto.
	* conform/Makefile (test-xfail-ISO/signal.h/linknamespace): Remove
	variable.
	(test-xfail-ISO99/signal.h/linknamespace): Likewise.
	(test-xfail-ISO11/signal.h/linknamespace): Likewise.
Remove ARM __GNUC_PREREQ(4,4) conditionals.

This patch removes conditionals in ARM code on __GNUC_PREREQ(4,4),
which were already obsolete even before the move from 4.4 to 4.6 as
minimum GCC version for building glibc.

Tested for ARM that installed shared libraries are unchanged by this
patch.

	* sysdeps/arm/sysdep.h [PROF && __GNUC_PREREQ(4,4)] (CALL_MCOUNT):
	Make definition conditional only on [PROF].
	[PROF && !__GNUC_PREREQ(4,4)] (CALL_MCOUNT): Remove conditional
	definition.
	[__GNUC_PREREQ(4,4)] (mcount): Make definition unconditional.
	[!__GNUC_PREREQ(4,4)] (mcount): Remove conditional definition.
Remove x86_64 __GNUC_PREREQ (4, 6) conditional.

This patch removes a conditional on __GNUC_PREREQ (4, 6) in x86_64
code.

Tested for x86_64 that installed shared libraries are unchanged by
this patch.  Committed (I think this file reasonably comes under math
maintainership).

	* sysdeps/x86_64/fpu/dla.h [__FMA4__ && __GNUC_PREREQ (4, 6)]
	(DLA_FMS): Make definition conditional only on [__FMA4__].
	[__FMA4__ && !__GNUC_PREREQ (4, 6)] (DLA_FMS): Remove conditional
	definition.
Remove sigvec.