Server uplink feature

[fragglet]

Currently it's possible to bridge a local ipxbox server to a LAN, but there's no way to bridge to an external server. In theory a standalone "uplink" program could bridge a LAN to a remote ipxbox server, and multiple users could do this to transparently connect their LANs and play together.

It would require an extension to the dosbox protocol since that assumes you only ever have a single machine with a MAC address supplied by the server.