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

[Eli Zaretskii]

> Date: Fri, 05 Aug 2022 08:21:30 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: Eli Zaretskii <eliz@gnu.org>, gerd.moellmann@gmail.com, 
>     56682@debbugs.gnu.org, monnier@iro.umontreal.ca
> 
> > BTW, 'M-> M-<' triggers some puzzling long wait (~3 seconds) both on 
> > master and with my change, every time I issue this sequence of commands.
> >
> 
> This is caused by show-paren-mode.

Interesting.  I guess the problematic part is the code in
show-paren-mode which searches for the matching parenthesis, not the
part that puts the overlay on the buffer?  IOW, does making
blink-matching-paren-distance smaller shortens the delay?