bug#651: suggestion: replace xpm images format by png

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Thu, 26 Sep 2019 20:15:22 +0200
> Cc: 651@debbugs.gnu.org
> 
> > In emacs, it seems the default image format is xpm.
> > http://en.wikipedia.org/wiki/X_PixMap
> >
> > For example, the emacs logo, widget graphics, all seems to be xpm
> > format at dir “etc/images/”.
> >
> > The xpm image format is some 19 years old tech based on ascii text,
> > very bulky. png or svg are perhaps good candidates.
> 
> The suggestion is 11 years old, but I still don't think this is
> something that we're going to do.  Emacs may be build without support
> for these other image formats, and it's still nice to show at least some
> icons.  So I'm closing this bug report.

Especially since we nowadays display SVG, PNG, XPM, or PBM, when
available and in that order.