[PATCH] X86-64: Add dummy memcopy.h and wordcopy.c

[Roland McGrath]

There's no reason for the header, since sysdeps/generic/memcopy.h is just a
header.  In an x86_64 build, nothing should #include it and so that's fine.

The files outside string/ that #include <memcopy.h> do so for no reason at
all and those lines should just be removed from all of them.

wordcopy.c is probably unused on several architectures.  One approach would
be to just drop it from routines in string/Makefile and add it via
sysdep_routines for machines that actually need it.  That doesn't seem
quite right because generic string/foo.c uses it, but every architecture
having a dummy file seems icky.