bug#6918: Colors of xbm image are swapped on Windows

[Eli Zaretskii]

> From: Jason Rumney <jasonrumney@gmail.com>
> Date: Fri, 27 Sep 2019 05:38:54 +0800
> Cc: Lars Ingebrigtsen <larsi@gnus.org>, kzhr@d1.dion.ne.jp, 
> 6918@debbugs.gnu.org
> 
> I wouldn't call myself an expert on images on Windows. I basically got it 
> working through trial and error, and
> from the looks of that history there may have been bugs fixed later that 
> invalidated some early decisions. Most
> of the monchrome Emacs icons were PBM IIRC, so XBM may not have had a lot of 
> testing on Windows over
> the past 12 years.

How do you suggest to test the proposed change, to make sure it
doesn't break something else?  Any pointers to those monochrome PBM
icons used in the past, for example, or any other files?

Or would you suggest to install the proposed change?

Thanks.