bug#81638: 32.0.50; flyspell-prog-text-faces type and semantics

> From: Stefan Monnier <[email protected]>
> Cc: Michael Heerdegen <[email protected]>,
>   [email protected],  [email protected]
> Date: Mon, 17 Aug 2026 14:16:56 -0400
> 
> > How about making a separate variant of flyspell-mode for these use
> > cases, then?  flyspell-prog-mode might be an approximation, but AFAIU
> > from what you are saying, it is not optimal, because you need to tweak
> > it in ways that was not meant to happen, and because LaTeX is not a
> > programming language anyway.  A new variant of flyspell would make
> > more sense, IMO.
> 
> `flyspell-prog-mode` was a kind of quick-hack and I think Michael's
> abuse of it just shows that this quick hack is useful more generally
> than its original motivation.
> 
> We could try and clean things up by renaming it, but it seems to me that
> a simpler solution is to improve the defcustom's `:type` to reflect more
> faithfully the values it can take (i.e. a list of `face` property
> values).

The request was much more general, and in particular he wanted to be
able to specify nil.

What I'm suggesting is to have a new flyspell-tex-mode, which will
cater to this and other similar cases.