Initial commit of the patch from the FreeBSD base (with its fixes).
This adds a module (for module-config in unbound.conf) dns64 that
performs DNS64 processing, see README.DNS64.
git-svn-id: https://unbound.nlnetlabs.nl/svn/trunk@3198 be551aaa-1e26-0410-a405-d3ace91eadb9