Follow-up to rP24728. This makes it possible to host without STUN via the lobby. You still have to setup your router, and STUN is still preferred.
The idea is that the lobby bots would answer the "register" GameList stanza with the hosted game and its IP as attribute, letting the client adjust its public IP.
There is a small window in which a client might try to join and the public IP isn't up, and the request goes through, but that seems rather unlikely to be a problem in practice.