cssselector: Make specificity handling a vfunc
cssselector: Make specificity handling a vfunc

The new region selector tracks more than just one soimple selector, so
it requires some more advanced specificity tracking.

Technically, this is still not correct, because it will report the same
specificity for
  tab:sorted
and
  tab:sorted:sorted
(and the second selector will be printed as the first) but this is
regions, so meh.

jigpu/gtk,jadahl/gtk,Lyude/gtk-,ahodesuka/gtk,ahodesuka/gtk,Lyude/gtk-,Adamovskiy/gtk,jadahl/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jigpu/gtk,grubersjoe/adwaita,jadahl/gtk,chergert/gtk,davidgumberg/gtk,davidgumberg/gtk,davidgumberg/gtk,jigpu/gtk,chergert/gtk,alexlarsson/gtk,grubersjoe/adwaita,chergert/gtk,jadahl/gtk,alexlarsson/gtk,ahodesuka/gtk,jigpu/gtk,grubersjoe/adwaita,chergert/gtk,Lyude/gtk-,alexlarsson/gtk,jadahl/gtk,Lyude/gtk-,Adamovskiy/gtk,jadahl/gtk,alexlarsson/gtk,Adamovskiy/gtk,Lyude/gtk-,jigpu/gtk,grubersjoe/adwaita,ahodesuka/gtk,chergert/gtk,ahodesuka/gtk,Adamovskiy/gtk,ahodesuka/gtk,davidgumberg/gtk,chergert/gtk,jigpu/gtk,davidgumberg/gtk,grubersjoe/adwaita,chergert/gtk,grubersjoe/adwaita,Lyude/gtk-,davidgumberg/gtk,Lyude/gtk-,jadahl/gtk,Adamovskiy/gtk,ahodesuka/gtk,Adamovskiy/gtk,alexlarsson/gtk,grubersjoe/adwaita,jigpu/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,jigpu/gtk,Lyude/gtk-,Adamovskiy/gtk,alexlarsson/gtk,ahodesuka/gtk,davidgumberg/gtk,alexlarsson/gtk,alexlarsson/gtk