* LocoLink scenarios:



At some level, we want the ability to say "LocoLink send 0-3" and "LocoLink 
receive 0-3". Probably functions in liblink.

1. LocoLink over a LapLink cable. The master expects to send data on D0,D1
  and receive on BUSY, ACK. The cable routes:

	D0   -> LL_CTL_ERROR
	D1   -> LL_CTL_ISELECT
	ACK  <- D3
	BUSY <- D4

2. LocoLink over a socket connection. The master expects to send data on 
  D0,D1 and receive on BUSY, ACK. The socket connection shows these up
  on the incoming side as D0,D1,BUSY,ACK.

