cssselector: Handle region selector like any selector
cssselector: Handle region selector like any selector

Instead of doing the previous match magic itself, use the
DESCENDANT_FOR_REGION hack and let that one do the magic.

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