Lay groundwork for rd/non-rd zone forwarding

Lay groundwork for rd/non-rd zone forwarding
make sure we can forward queries for certain zones to IPv6 as well as IPv4, syntax is:
 --forward-zones=google.com=2001:b18:0:1000:2e0:81ff:fe61:ae0d or even:
 --forward-zones=google.com=[2001:b18:0:1000:2e0:81ff:fe61:ae0d]:53
Thanks to Wijnand Modderman for discovering this problem.

Please note that the syntax above will not *yet* give you automatic ipv6
google via sixxs, slightly more work is needed for that.

git-svn-id: svn://svn.powerdns.com/pdns/trunk/pdns@1349 d19b8d6e-7fed-0310-83ef-9ca221ded41b