bug#67794: 30.0.50; mouse-face is not respected on SVG images

[Eli Zaretskii]

> From: Manuel Giraud <manuel@ledu-giraud.fr>
> Cc: alan@idiocy.org,  gerd.moellmann@gmail.com,  67794@debbugs.gnu.org
> Date: Wed, 20 Dec 2023 18:53:41 +0100
> 
> > It would be a shame to waste cycles on PNG images as long as we don't
> > solve this problem, so I'd prefer to enable this only for SVG and
> > leave a FIXME comment about PNG.
> 
> Here is an updated version of this patch:
> 
>      - I had to export 'image_spec_value' from image.c to use it in
>        xdisp.c
>      - I also guard this feature behind a #ifdef HAVE_RSVG

Thanks, installed on master, and closing the bug.