rewrote nmbd's wins backend to use a tdb instead of a flat text file.

rewrote nmbd's wins backend to use a tdb instead of a flat text file.
Changed the way the wins record are handled in memory. Now they are living
much longer with the different states: active, released and tombstone.
Also added a version ID, some wins flags and the wins owner ip address to
the namrec->data struct, and a function to process messages sent by the
wins replication daemon.

the initiate_wins_processing() function is not correct, I'll fix it later.

        J.F.