Converted to call lib/wins_srv.c:wins_srv_ip() instead of lp_wins_server()

Converted to call lib/wins_srv.c:wins_srv_ip() instead of lp_wins_server()
when looking up the WINS server address.

Please *don't* use lp_wins_server() any more!

The wins_srv_ip() function has the following features:

- If the WINS server was entered as a DNS name then the translation to an
  IP address will already have taken place.  We used to do this every time
  a call to the WINS server was made.  Ick.

- The return value of wins_srv_ip() is a struct in_addr.  Ready to go.

- When WINS failover is fully implemented, you'll be able to enter a colon-
  separated list of WINS servers via the WINS SERVER parameter.  Using
  lp_wins_server() directly will fail if this syntax is used.

Chris -)-----
(This used to be commit 56be7c2a49a8a918318a70843fff4e89ec10d0d3)