bug#17663: 24.4.50; arc-mode.el has unrar-free hard-coded

[Eli Zaretskii]

> From: Nicolas Petton <nicolas@petton.fr>
> Cc: monnier@iro.umontreal.ca, 17663@debbugs.gnu.org
> Date: Wed, 30 Sep 2015 14:06:05 +0200
> 
> > Given the troubled history of the Free Software programs available to
> > access RAR archives, and its various format versions, I'd prefer that
> > we had more than one solution for RAR.  Having just one hard-coded
> > program sounds like a near-term maintenance headache.  Other
> > possibilities include unrar-free, GNA's unrar, and bsdtar from
> > libarchive.  I think we should make this more future-proof.  Nicolas,
> > would you like to work on that?
> 
> Would adding support for (GNA) unrar be enough for you?
> If so, I'll gladly add it.

Sure, please do, and thanks.