Make symbolic icons work with the current rsvg
Make symbolic icons work with the current rsvg

The rsvg loader now restricts what external files it will
allow to load from an svg. Thus our xinclude trick doesn't work
anymore. To work around that, embed the payload in a  data: uri.
This is somewhat ugly, but it is what GTK+ does.

DoctorJellyface/gnome-themes-standard,Distrotech/gnome-themes-standard,Distrotech/gnome-themes-standard,DoctorJellyface/gnome-themes-standard