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

[Eli Zaretskii]

> From: Pip Cet <pipcet@gmail.com>
> Date: Sun, 30 Jun 2019 09:48:31 +0000
> Cc: triska@metalevel.at, 36337@debbugs.gnu.org
> 
> +A string or a bool-vector containing the bits of the image (plus
> +perhaps some extra bits at the end that will not be used).  It should
> +contain at least @var{stride} * @code{height} bits, where @var{stride}
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This should be @w{@code{@var{stride} * @code{height}}}, sorry I didn't
notice this before.

Otherwise, this LGTM, thanks.