bug#58342: 29.0.50; noverlay branch is O(N) for important calls

[Matt Armstrong]

Drew Adams <drew.adams@oracle.com> writes:

>> For the potential performance problem with next-overlay-change to appear
>> you need overlays to overlap, so not something like linum or nhexl-mode.
>
> Which is why I mentioned zones.el.
>
> And I don't expect it to be alone in this.
> Overlays can be anywhere.

For what it is worth, the use cases where this bug applies are likely to
be noticeably slow in Emacs today as well.