Remove sysdeps/nptl/configure.ac.

sysdeps/nptl/configure.ac tests for forced unwind support and the C
cleanup attribute, giving errors if either is unsupported.  It does
nothing beyond running those two tests.

Both the attribute, and _Unwind_GetCFA which is used in the forced
unwind test, were added in GCC 3.3.  Thus these tests are long
obsolete, and this patch removes the configure fragment running them,
along with associated conditionals.

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

	* sysdeps/nptl/configure.ac: Remove file.
	* sysdeps/nptl/configure: Remove generated file.
	* configure.ac (libc_cv_forced_unwind): Do not substitute.
	* configure: Regenerated.
	* config.h.in (HAVE_FORCED_UNWIND): Remove #undef.
	* config.make.in (have-forced-unwind): Remove variable.
	* nptl/Makefile [$(have-forced-unwind) = yes]: Make code
	unconditional.
	* nptl/descr.h [HAVE_FORCED_UNWIND]: Likewise.
	* nptl/unwind.c [HAVE_FORCED_UNWIND]: Likewise.
	(__pthread_unwind) [!HAVE_FORCED_UNWIND]: Remove conditional code.
	* nptl/version.c [HAVE_FORCED_UNWIND]: Make code unconditional.
	* sysdeps/nptl/Makefile [$(have-forced-unwind) = yes]: Make code
	unconditional.