CFT: final patches for NGROUPS>>16

[ttw+bsd at cobbled.net]

posted patches to this effect some months ago.  they needed some
clean-up and validation but the also mapped correctly into an
RPC_NGROUPS_MAX and IPC_NGROUPS_MAX for consistent (and possibly
dynamic) mapping to those problem areas.  they build and run but are
untested beyond that.  i do not expect to have time to re-visit the
problem in reasonable order.  they also included some other userland
changes that may be of interest.