bug#57804: An infinite loop in a `fontify-region' function causes Emacs to hang indefinitely

[Gregory Heytings]

> who then when presented with a real-world failure suggests the aggrieved 
> module ought to accommodate his long lines fix

It was clear from the very beginning that the long line fixes would break 
some code in unusual circumstances, and that such code would have to be 
adapted.  That is unavoidable, except of course with frozen programs such 
as the TeX engine.