bug#56682: Fix the long lines font locking related slowdowns

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: 56682@debbugs.gnu.org,  Eli Zaretskii <eliz@gnu.org>,
>   gregory@heytings.org,  monnier@iro.umontreal.ca
> Date: Sat, 23 Jul 2022 17:01:02 +0200
> 
> And the new lottery numbers on the feature branch are:
> 
> Font-lock Scroll-bar Composition Output
> ------------------------------------------------------------
> on      on         on          GCs: 14 Elapsed time: 7.276626 seconds
> on      off        on          GCs: 1 Elapsed time: 5.363002 seconds
> on      off        off         GCs: 1 Elapsed time: 3.967520 seconds

Thanks.  How about now, after I installed the last change?