Update some network headers and add minimal getnameinfo and setgroups

[Christian Mauderer]

The first four patches add a minimal getnameinfo and a dummy for
setgroups. This allows some applications to build (e.g. civetweb). I
already sent these patches a few weeks ago. The new version only
contains a bugfix. The original patches are here:
https://lists.rtems.org/pipermail/devel/2016-May/014797.html

The rest of the patches are updating some of the network headers of the
old network stack. They are replaced with clean versions from current
FreeBSD. This allows libressl to build.

Further the replaced headers are now (mostly) identical to the ones used
in the new network stack. This could simplify the process of moving the
old network stack to it's own repository if we ever decide to do that.