dynamic dns updates from WINS

[tridge at linuxcare.com]

I've just added the ability for nmbd to call an external program when
changes happen to the WINS database in a Samba WINS server. See the
option "wins hook" in Samba 2.0.6 when it is released. An example
script that calls the nsupdate dynamic DNS update program is provided.

Hopefully this will be useful for sites that want their dynamic
windows boxes to show up in DNS.

Cheers, Tridge