bug#58021: 29.0.50; Remove old font.c code

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Manuel Giraud <manuel@ledu-giraud.fr>,  58021@debbugs.gnu.org
> Date: Fri, 23 Sep 2022 17:41:43 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > FWIW, I see no reason to remove this.  Someone someday may decide to
> > implement these ideas.
> 
> Perhaps we could pick it out and place on a branch?  Because it's a lot
> of deaf stuff to wade through when looking at font.c.

Would it help if we move that to the end of the file?

My primary motivation for leaving this is to try to attract someone to
get involved in maintaining and developing font.c and fontset.c.
We've all but lost our only expert on this, and leaving this part of
Emacs without an active maintainer is bad for us.  I might even add a
comment there that encourages people to finish implementation of at
least some of that stuff, in the hope that this will bring on board
someone capable and motivated.