Bug 781020 - GIMP UI vector icons are drawn way too small.
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.