 * Add the no_inherit flag to _all_ options. (maybe call it "clear" or
   similar?)
 * cleanup the current code a little
 * speed up transparent fills (reuse the GdkPixbuf, or maybe some other way?)

Big things:
 * cairo port, what we need for this is:
   - acceleration of the most important image operations (scaling,
     composition of RGBA images)
   - some bugs to be fixed (need to investigate if some have been fixed
     already)

arch-tag: 45211614-40fb-4fb6-adaa-d0f8235c2841
