Character echo at read time

[Guy Harris]

> Of course, it SHOULD flush input.  Presumably, if you're going to discard
> output, there would be few cases if you had input queued up and
> fewer cases where you'd want that queued input read.

Why should it flush input?  As far as I know, it didn't do so in the DEC OSes
from which it was derived; those times when I used ^O under RT-11 I never had
any input queued so it wouldn't have made any difference whether it did or
didn't, and not doing so is presumably simpler.

(I don't know that I've ever used ^O under UNIX, except when testing tty
drivers.  There's a problem with it in UNIX that is less severe under the
aforementioned DEC OSes: ^O was in the DEC OSes far enough back in history
that applications that wanted to *force* messages to appear already did the
magic special function to do so.  However, it was grafted onto some versions of
UNIX after the fact, so most applications that might want to force a message to
appear don't know how to do so and, thus, don't do so.)