* config.h.in (USE_MULTIARCH): Define.

* config.h.in (USE_MULTIARCH): Define.

	* configure.in: Handle --enable-multi-arch.
	* elf/dl-runtime.c (_dl_fixup): Handle STT_GNU_IFUNC.
	(_dl_fixup_profile): Likewise.
	* elf/do-lookup.c (dl_lookup_x): Likewise.
	* sysdeps/x86_64/dl-machine.h: Handle STT_GNU_IFUNC.
	* elf/elf.h (STT_GNU_IFUNC): Define.
	* include/libc-symbols.h (libc_ifunc): Define.
	* sysdeps/x86_64/cacheinfo.c: If USE_MULTIARCH is defined, use the
	framework in init-arch.h to get CPUID values.
	* sysdeps/x86_64/multiarch/Makefile: New file.
	* sysdeps/x86_64/multiarch/init-arch.c: New file.
	* sysdeps/x86_64/multiarch/init-arch.h: New file.
	* sysdeps/x86_64/multiarch/sched_cpucount.c: New file.

	* config.make.in (experimental-malloc): Define.
	* configure.in: Handle --enable-experimental-malloc.
	* malloc/Makefile: Handle experimental-malloc flag.
	* malloc/malloc.c: Implement PER_THREAD and ATOMIC_FASTBINS features.
	* malloc/arena.c: Likewise.
	* malloc/hooks.c: Likewise.
	* malloc/malloc.h: Define M_ARENA_TEST and M_ARENA_MAX.