r12976: Patch from Brad Henry <j0j0@riod.ca>:

r12976: Patch from Brad Henry <j0j0@riod.ca>:

This patch pulls the AD site name generation and site join code from
libnet/libnet_join.c and puts it into a new file, libnet/libnet_site.c.
This way, a common means for site name, configuration dn and server dn
generation exists so it doesn't need to be rewritten in new code (such
as the future libnet_leave for example).

I've made a couple of changes, but nothing dramatic.  Nice work Brad!

Andrew Bartlett
(This used to be commit 45f67b3f6d506cc8cb9922184a8c0c9b59a8f702)