bug#63253: 29.0.90; with-delayed-message fails in combination with inhibit-message

[Stefan Monnier]

> Or maybe (or in addition) regex-emacs.c should save and restore its
> state around calls to maybe_quit?  Is that possible?

That would be very costly, I think.
But maybe `gl_state` can be turned into an array (stack) of states, or
can be stack-allocated, so that when we can do nested regexp
matches safely.

There's still the issue that `set-message-functions` could theoretically
do nasty things like insert/delete text in the current buffer, leading
to `regexp.c` containing stale pointers to the old text.


        Stefan