x86-64: Use IFUNC memcpy and mempcpy in libc.a

Since apply_irel is called before memcpy and mempcpy are called, we
can use IFUNC memcpy and mempcpy in libc.a.

	* sysdeps/x86_64/memmove.S (MEMCPY_SYMBOL): Don't check SHARED.
	(MEMPCPY_SYMBOL): Likewise.
	* sysdeps/x86_64/multiarch/ifunc-impl-list.c
	(__libc_ifunc_impl_list): Test memcpy and mempcpy in libc.a.
	* sysdeps/x86_64/multiarch/memcpy-ssse3-back.S: Also include
	in libc.a.
	* sysdeps/x86_64/multiarch/memcpy-ssse3.S: Likewise.
	* sysdeps/x86_64/multiarch/memmove-avx512-no-vzeroupper.S:
	Likewise.
	* sysdeps/x86_64/multiarch/memcpy.c: Also include in libc.a.
	(__hidden_ver1): Don't use in libc.a.
	* sysdeps/x86_64/multiarch/memmove-sse2-unaligned-erms.S
	(__mempcpy): Don't create a weak alias in libc.a.
	* sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S: Support
	libc.a.
	* sysdeps/x86_64/multiarch/mempcpy.c: Also include in libc.a.
	(__hidden_ver1): Don't use in libc.a.