Remove configure tests for -mno-vzeroupper support.

GCC added support for -mno-vzeroupper in version 4.6.  Thus the
configure tests for this support 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_novzeroupper): Remove
	configure test.
	* sysdeps/i386/configure: Regenerated.
	* sysdeps/x86_64/configure.ac (libc_cv_cc_novzeroupper): Remove
	configure test.
	* sysdeps/x86_64/configure: Regenerated.
	* sysdeps/x86_64/Makefile [$(config-cflags-novzeroupper) = yes]:
	Make code unconditional.