It's not finished yet, but I have already added all the individual
Freedesktop and GTK+ icons. The goal will be to have all the Symbolic
icons in this one file so that in the future we can just extract
individual SVG files from object IDs.
This was the original plan but librsvg was just too buggy and would not
extract the proper viewbox for some icons. Fortunately it seems that the
bug reports I made are finally starting to be taken into account so I am
hoping for a usable librsvg soon and starts the work which should have
been done from the start.