r14421: This does two things

r14421: This does two things

* Automatically creates the BUILTIN\Users group similar to
  how BUILTIN\Administrators is done.  This code does need to
  be cleaned up considerably.  I'll continue to work on this.

* The important fix is for getusergroups() when dealing with a
  local user and nested groups.  Now I can run the following
  successfully:

    $ su - jerry -c groups
    users BUILTIN\users
(This used to be commit f54d911e686ffd68ddc6dbc073987b9d8eb2fa5b)