bug#8355: 24.0.50; Boxes in mode-line and scrolling

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: antoine.levitt@gmail.com,  8355@debbugs.gnu.org
> Date: Mon, 14 Dec 2020 20:05:06 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Thanks, this should now be fixed on the master branch.
> 
> Wonderful!  Seems to work perfectly.

The scary thing about this fix is that the problematic code was in a
very low-level function, which is used all over the place, and that
code didn't change since Emacs 21.  So I wonder/dread what other
effects will this change have...