[DALnet-src] usermod and spam

Hello, I got the idea, if possible, implementing some features to bahamut, for users to deal with spam. The idea is, adding a user mode, if enabled, all incoming msg with the pattern http* and www* will be blocked, if the sender is unregistered, Since most of spam I've seen, spam bots, are unregistered, so, registered users can override the mode. thanks