Add support for multiplayer (irDA, BT, USB, TCP, etc.)

[XerTheSquirrel]

Palm supports capabilities for beaming and otherwise. It is possible for multiplayer to be added to the core.

• If using the RetroArch network, Mu will have to have a minimum amount of globals where multiple devices can be emulated at the same time with controller input. This might end up being lots of effort but definitely should be possible.
• Otherwise off band TCP could just send signals over TCP.