configure.ac: Substitute CPU_OPT_EXT_RANDOM.

	* configure.ac: Substitute CPU_OPT_EXT_RANDOM.
	* configure.host: Define cpu_opt_ext_random to location of the
	optimized version of <ext/random>.
	* include/Makefile.am (ext_headers): Add ${ext_host_headers}.
	(ext_host_headers): Define.
	* include/ext/random (simd_fast_mersenne_twister_engine<>
	::operator==): Don't define function here.
	* include/ext/random.tcc (simd_fast_mersenne_twister_engine): Don't
	define code using SSE2 here.  Define generic code only if
	_GLIBCXX_OPT_HAVE_RANDOM_SFMT_GEN_READ is not defined.
	(simd_fast_mersenne_twister_engine<>
	::operator==): Define here if
	_GLIBCXX_OPT_HAVE_RANDOM_SFMT_OPERATOREQUAL is not defined.
	* config/cpu/generic/opt/ext/opt_random.h: New file.
	* config/cpu/i486/opt/ext/opt_random.h: New file.
	* libsupc++/Makefile.in: Regenerated.
	* testsuite/Makefile.in: Regenerated.
	* po/Makefile.in: Regenerated.
	* configure: Regenerated.
	* Makefile.in: Regenerated.
	* doc/Makefile.in: Regenerated.
	* aclocal.m4: Regenerated.
	* python/Makefile.in: Regenerated.
	* include/Makefile.in: Regenerated.
	* src/c++98/Makefile.in: Regenerated.
	* src/c++11/Makefile.in: Regenerated.
	* src/Makefile.in: Regenerated.

From-SVN: r191384