environ and __progname are not declared in a public header; declare them
in libc's hidden/stdlib.h instead of in each .c file that needs one

ok deraadt@ gsoares@ mpi@

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@

Add errc/verrc/warnc/vwarnc family: versions of err/... that take the errno
value to use for the strerror() message as an argument. Originally from
FreeBSD 3.0

Patch from Steffen Nurpmeso (sdaoden (at) gmail.com) with minor tweaks.