Mostly-working ethernet and various changes

This may break the linux/windows builds - I haven't tried to compile
on those platforms yet.

- Ethernet is more or less working with a hardcoded /dev/tun0 network interface
and hardcoded MAC address, though there's no automatic ifconfig/route
configuration yet.

- Instructions TAS and ILLEGAL are implemented now

- Fixed some bugs in MOVEP

- Implemented some other instruction disassemblers

- Other little changes