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@