IPv6: post-integration fixes

The most glaring errors only show up after merging. /blame @self

ip_equal(): lost the check for same family somewhere on the road, readded and now also testing for IPv4-in-IPv6 embedded if the two families are AF_INET + AF_INET6

addr_resolv(): on rewrite, introduced bad copy&paste error in AF_UNSPEC (dual-stack) => IPv4 case