bug#57434: 28.1.91; Terminal Emacs Mac OS flickering.

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: kuragin@google.com,  57434@debbugs.gnu.org
> Date: Sat, 03 Sep 2022 10:04:14 +0200
> 
> Gerd Möllmann <gerd.moellmann@gmail.com> writes:
> 
> > Eli Zaretskii <eliz@gnu.org> writes:
> >
> >> Actually, I think we'll need one more small change.  These hooks are
> >> called from update_begin and update_end like this:
> >
> > Dmitrii, do you want to try implementing that?
> 
> Searching the web for "emacs synchronized updates" turned up this patch,
> which you could try
> 
> https://gist.github.com/Patryk27/c7b9dac8113f4ccdb2ef74e0083d9d41

Just without the explicit calls to fflush, please.  I think that's
there to cover for the bug in update_frame which I mentioned before.