[GreenKeys] USB to TTY-loop possibility...

[epvgk at limpoc.com]

Btw i'm not trying to make a half duplex tty look like a full duplex device
to the OS. That's too hard and needs to know too much about the expected data
flow. It will of course work fine in actual full duplex on separate send and
receive loops. 

I did some sort of minimal work on pseudo-full-duplex for a specific 
application (an IRC client) by keeping track of characters sent and expected
to be echoed back, and doing "echo suppression" with fuzzy matching on whole
lines of text, but it's imperfect and probably not going to get any better... 

eric