r23471: Here's a rough patch for expanding domain group membership

r23471: Here's a rough patch for expanding domain group membership
in the winbindd_getgrnam() call.  Couple of comments:

* Adds "winbind expand groups" parameter which defines the
  max depth winbindd will expand group members.  The default
  is the current behavior of one level of expansion.
* The entire getrgnam() interface should be async.  I
  haven't done that.
* Refactors the domain users hack in fill_grent_mem() into
  its own function.
(This used to be commit 3d3a8130351753dc5caa2a270d130e2150da6b54)