bug#36337: 26.1; XBM images are sometimes not displayed correctly

[Eli Zaretskii]

> From: Pip Cet <pipcet@gmail.com>
> Date: Sat, 29 Jun 2019 07:20:26 +0000
> Cc: triska@metalevel.at, 36337@debbugs.gnu.org
> 
> > I'm not sure I understand what you mean, exactly.  Can you show an
> > example of the new API?
> 
> No major changes, just that :stride is passed in along with :height
> and :width (optional for now, but strongly recommended by the
> documentation). See attached patch.

Fine with me, but please indent with indent-tabs-mode set to non-nil,
to be consistent with the surrounding indentation.

Also, this change needs to be called out in NEWS.

Thanks.