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

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Dmitry Gutov <dgutov@yandex.ru>,  56682@debbugs.gnu.org,
>   gregory@heytings.org
> Date: Tue, 16 Aug 2022 10:11:57 -0400
> 
> Eli Zaretskii [2022-08-16 17:07:46] wrote:
> >> >> The locked narrowing prevents that "last mile", sadly.
> >> > Nonsense, it doesn't prevent any such things.
> >> > Let's not exaggerate when we try to make a point, okay?
> >> Why nonsense?
> > Because it takes no effort to override it and then try changes in any
> > major mode.
> 
> AFAIK it requires recompiling Emacs

No, it doesn't.