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

[Gregory Heytings]

> > Anyway, could you please try the combined patch I posted recently 
> > together with dictionary.json?
> >
> > https://debbugs.gnu.org/cgi/bugreport.cgi?bug=56682#1084
>
> Gregory, could you do this?
>
> And report on how your own responsiveness metrics hold up after that.

Now done, see my reply on emacs-devel.