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

[Stefan Monnier]

>> Do you happen to know via which path it can be called (beside the obvious
>> ones when the redisplay ends up calling ELisp, such as via jit-lock)?
>
>  pos_visible_p
>   -> previous-single-char-property-change

Ah, thanks, indeed.  Hadn't noticed this one.

>  set_point_both
>   -> previous-char-property-change
>       -> previous-overlay-change

I knew about this one but AFAIC it doesn't count :-) because it's only
triggered when `inhibit-point-motion-hooks` is nil, and this var has
defaulted to t (and been marked obsolete) since Emacs-25.


        Stefan