Hi! I would like to introduce myself to the list and provide a patch for review. I'm novalis_dt on Sourceforge. I know Bryce from when he worked on the Worldforge project. I have recently started using Inkscape -- I'm not much of an artist, but I redid the front page of my website with Inkscape. I've also done a couple of diagrams for work (I do licensing for the Free Software Foundation). I've submitted a couple of other minor patches, and now have CVS commit access.
This patch provides a new command: "Vacuum unused defs." SVG files can accumulate cruft -- gradients, markers, etc, which aren't in use. I've chosen to make this command manual, because sometimes, you'll want to keep this cruft for later usage. But if you want smaller SVG files, for web usage (or secrecy reasons), you might try this feature.
When I wrote the first version of this patch, I didn't understand the SPObject tree. I think I do now. I'm somewhat baffled that there's no sp_object_get_child_by_tagName function already -- am I just missing it? If not, it probably belongs in sp-object.cpp, but I didn't want to put it there prematurely.
If I hear no objections, I'll commit it in a few days.