Add WITH_WINBIND_NSS knob, which will cause nss_winbind to be installed.
Currently only the getpwent(3) and getgrent(3) family of functions are
supported.
o Respect CFLAGS.
o Add a message telling users to take out -O from their CFLAGS and
recompile/reinstall samba if they encounter problems.
PR: ports/45691
Approved by: dwcjr (MAINTAINER)