Remove configure tests for SSE4 support.

Remove configure tests for SSE4 support.

GCC added support for -msse4 in version 4.3.  Thus the configure tests
for it are obsolete, and this patch removes them.

Tested for x86_64 and x86 (testsuite, and that installed stripped
shared libraries are unchanged by this patch).

	* sysdeps/i386/configure.ac (libc_cv_cc_sse4): Remove configure
	test.
	* sysdeps/i386/configure: Regenerated.
	* sysdeps/i386/i686/multiarch/Makefile
	[$(config-cflags-sse4) = yes]: Make code unconditional.
	* sysdeps/i386/i686/multiarch/strcspn.S [HAVE_SSE4_SUPPORT]:
	Likewise.
	* sysdeps/i386/i686/multiarch/strspn.S [HAVE_SSE4_SUPPORT]:
	Likewise.
	* sysdeps/x86_64/configure.ac (libc_cv_cc_sse4): Remove configure
	test.
	* sysdeps/x86_64/configure: Regenerated.
	* sysdeps/x86_64/multiarch/Makefile [$(config-cflags-sse4) = yes]:
	Make code unconditional.
	* sysdeps/x86_64/multiarch/strcspn.S [HAVE_SSE4_SUPPORT]:
	Likewise.
	* sysdeps/x86_64/multiarch/strspn.S [HAVE_SSE4_SUPPORT]: Likewise.
	* config.h.in (HAVE_SSE4_SUPPORT): Remove #undef.