multiple IPXWrapper processes without needing a shared router thread.
Replaced router/rclient code with a single, per-process router thread.
Add addresses to the cache in the router main loop rather than winsock recv
functions.
Packets are no longer preceeded by an rpacket_header structure when relayed to
the local UDP sockets.
Each IPXWrapper instance creates a "private" UDP socket bound to a random port
on INADDR_ANY which is used for sending all packets and receiving unicast.
Bugfix: Check source socket number before relaying to a connected socket.
