bug#34535: 27.0.50; emacs -nw: while-no-input + sit-for + <KEY> => Quit

[Stefan Monnier]

> IOW, I think while-no-input does not (and cannot) reliably produce
> deterministic output in the case where BODY itself reads input.  We
> try to DTRT, but there can be no general guarantees in these cases.

Thanks, Eli.  Indeed, "TRT" is not even clear here.
Some things are clearly not right, but if we look a bit further it
quickly gets murky.

Regarding your patch.  I'm not sure it's "TRT" but given the murky/messy
context it looks good to me.  Hopefully at some point someone can sit
down and think through the whole way we handle "quit" and try to clean
it up.


        Stefan