bug#57727: 29.0.50; Optimize tty display updates

[Eli Zaretskii]

> Cc: 57727@debbugs.gnu.org
> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Date: Tue, 13 Sep 2022 07:53:47 +0200
> 
> How can we proceed?  What do the maintainers think?  I could also just
> put in on a branch, for later.

I'm okay with having this on master.  We can always fine-tune it
later, given that we get some feedback.

Lars?