Though the bug was mostly fixed, it seems to still happen on Windows XP,
where apparently no content type had been registered for SVG.
GTK+ developers don't seem too keen to patch GTK+ 2.24 for a platform
which they don't support anymore.
Also if not mistaken, GIMP does not officially support Windows XP
anymore either. A patch though has already been provided by Edward E.
and it really doesn't look like it could break anything since it just
adds a last "else if" when everything else failed (and inside a #ifdef
affecting only WIN32 builds).
So let's just add it in our builds at least. We still don't have support
for it, but I see no reason to just refuse a minor patch which won't
break anything else.
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