All code which was using ip and port now uses a new IPv4 object,
subclass of a new network_address class. This will allow easy
addition of I2P addresses later (and also IPv6, etc).
Both old style and new style peer lists are now sent in the P2P
protocol, which is inefficient but allows peers using both
codebases to talk to each other. This will be removed in the
future. No other subclasses than IPv4 exist yet.
