bug#27872: 26.0.50; freeze when opening file with emojis

[Eli Zaretskii]

> From: Nejc Vivod <nvivod@gmail.com>
> Date: Sun, 30 Jul 2017 15:09:04 +0200
> Cc: 27872@debbugs.gnu.org
> 
> Yeah, I tried running with -Q; I’ve also reran it from lldb with this arg, 
> attaching the backtrace. I’ve got quite a few fonts installed, could that be 
> an issue?

Alan, it might help to add some printf in macfont_list that would log
on a file all the fonts that are being scanned there.  Maybe that will
give some hint.