libc: Avoid defining memcpy() as a macro under FORTIFY_SOURCE

[markj]

Summary

Otherwise it is impossible to make certain memcpy() usages work, e.g.,
memcpy(dst, &(struct foo){1, 2}, sizeof(*dst)) fails to compile
because a macro parameter can't contain a comma. This arises when
compiling graphics/mesa-libs with FORTIFY_SOURCE enabled.

[markj]

@kevans do you have any time to look at this?

[kevans]

It should probably be noted that this effectively orphans the corresponding __*_chk symbols in libc/secure. I don't think that's a bad thing or that we should stop exposing a default version for them, it just means that we won't emit references to them with our own implementation.

include/ssp/string.h

123–126

I think we probably want __ssp_redirect_raw_impl for these two like we do in <ssp/wchar.h>; the easy __ssp_redirect* loses runtime overlap checks for src/dst that are currently done by the __*_chk symbols