tty driver features

[guy at rlgvax.UUCP]

Actually, t_brkc goes back to V7 (as do several other things in 4.1BSD), and
the USG driver has an equivalent; both of them echo the character, however.
If it weren't echoed, you could also set it to ESC and use it for TENEX-style
command completion and for TECO...

Why not add another ECHO? bit to the USG driver; it already has 4 of them.
Unfortunately, ECHONL doesn't mean "don't echo NL if it's off", but means
"echo an NL even if ECHO is off".

	Guy Harris
	RLG Corporation
	{seismo,mcnc,we13,brl-bmd,allegra}!rlgvax!guy