Add start of IPv6 implementation. Currently most of this is avoiding

Add start of IPv6 implementation. Currently most of this is avoiding
IPv6 in winbindd, but moves most of the socket functions that were
wrongly in lib/util.c into lib/util_sock.c and provides generic
IPv4/6 independent versions of most things. Still lots of work
to do, but now I can see how I'll fix the access check code.
Nasty part that remains is the name resolution code which is
used to returning arrays of in_addr structs.
Jeremy.
(This used to be commit 3f6bd0e1ec5cc6670f3d08f76fc2cd94c9cd1a08)