So far, we're able to override the bridges for SVG 1.0/1.1, but not for SVG 1.2.
Attached is a proposal for a new method to allow this, even for future versions
of SVG. Backwards-compatibility is preserved.
PS: The patch also contains a nit for the CleanerThread which is a little
anonymous right now. With this patch it gets its own name and debuggers know who