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

[Gregory Heytings]

> > > Cache existence is not guaranteed.
> >
> > Can that cache not be created unconditionally when the Org file is 
> > opened?
>
> Without cache, the parser will have to process everything on every 
> request to determine object at point.

I'm not sure I understand what you mean?  If the cache is created when the 
Org file is opened and updated when necessary, its existence becomes 
guaranteed, no?