bug#57207: 29.0.50; Fontification is slow after e7b5912b23 (Improvements to long lines handling)

[Eli Zaretskii]

> Cc: 57207@debbugs.gnu.org, yantar92@gmail.com
> Date: Thu, 18 Aug 2022 17:10:51 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> But a momentary narrowing does happen, and it comes from here:
> 
> 
>       safe_run_hooks_maybe_narrowed (Qpre_command_hook,
>                                    XWINDOW (selected_window));
>   [...]
> 
>       safe_run_hooks_maybe_narrowed (Qpost_command_hook,
>                                    XWINDOW (selected_window));

I guess we need unwind-protect inside safe_run_hooks_maybe_narrowed?