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

[Gerd Möllmann]

Eli Zaretskii <eliz@gnu.org> writes:

> on long-line.xml produces a 15-fold slowdown with font-lock turned on
> as compared to its being turned off (203 sec vs 13 sec).
>
> This is an unoptimized build, so you will probably see times that are
> 4 times faster, but I'd be interested in the relative times on your
> system.  Any explanations of the slowdown are also welcome.

MacOS 12.5, M1 chip
Head: 792734a6e2cd5558debc8d9fe95d34cb3e809fa4 Improve efficiency of DND
tooltip movement
./configure --with-native-compilation

The long-lines.xml is 313295 bytes.  Hope that's the right one.

Font-lock       Output
------------------------------------------------------------
on              GCs: 14 Elapsed time: 7.880788 seconds
off             GCs: 2 Elapsed time: 0.885791 seconds