Pull in namespace.h when building all .c files using gcc's -include option,
so that we can provide asm labels for the memcpy/memset/__stack_smash_handler
calls that it generates ab initio. Eliminate direct #includes of it. Make
sure it's a dependency of all objects (unnecessary for asm, but close enough).

ok deraadt@

Add framework for resolving (pun intended) libc namespace issues, using
wrapper .h files and asm labels to let internal calls resolve directly and
not be overridable or use the PLT. Then, apply that framework to most of
the functions in stdio.h, string.h, err.h, and wchar.h. Delete the
should-have-been-hidden-all-along _v?(err|warn)[cx]? symbols while here.

tests clean on i386, amd64, sparc64, powerpc, and mips64

naming feedback from kettenis@ and millert@
ok kettenis@