gdkwindow: Simplify invalidation
gdkwindow: Simplify invalidation

Now that all windows are non-opaque we can simplify the invalidation
a lot. There is no need to clip the invalidate area to child regions,
because we will always redraw everything under all the children.
We only have to handle native childen specially.

jigpu/gtk,Distrotech/gtk2,chergert/gtk,jessevdk/gtk,jadahl/gtk,Sidnioulz/SandboxGtk,jigpu/gtk,jessevdk/gtk,ahodesuka/gtk,grubersjoe/adwaita,jadahl/gtk,alexlarsson/gtk,Lyude/gtk-,ahodesuka/gtk,davidgumberg/gtk,davidgumberg/gtk,alexlarsson/gtk,grubersjoe/adwaita,Distrotech/gtk2,Adamovskiy/gtk,chergert/gtk,jigpu/gtk,Adamovskiy/gtk,alexlarsson/gtk,alexlarsson/gtk,alexlarsson/gtk,ebassi/gtk,chergert/gtk,Lyude/gtk-,chergert/gtk,alexlarsson/gtk,jessevdk/gtk,davidgumberg/gtk,jadahl/gtk,jigpu/gtk,alexlarsson/gtk,ebassi/gtk,jessevdk/gtk,chergert/gtk,grubersjoe/adwaita,jigpu/gtk,grubersjoe/adwaita,jadahl/gtk,bratsche/gtk-,jigpu/gtk,davidgumberg/gtk,Adamovskiy/gtk,jessevdk/gtk,chergert/gtk,ebassi/gtk,ebassi/gtk,Sidnioulz/SandboxGtk,ahodesuka/gtk,davidgumberg/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jigpu/gtk,ahodesuka/gtk,grubersjoe/adwaita,msteinert/gtk,ahodesuka/gtk,Lyude/gtk-,Adamovskiy/gtk,jadahl/gtk,msteinert/gtk,bratsche/gtk-,Distrotech/gtk2,bratsche/gtk-,jadahl/gtk,chergert/gtk,ebassi/gtk,msteinert/gtk,Sidnioulz/SandboxGtk,Lyude/gtk-,jadahl/gtk,jessevdk/gtk,msteinert/gtk,Lyude/gtk-,davidgumberg/gtk,Sidnioulz/SandboxGtk,davidgumberg/gtk,bratsche/gtk-,msteinert/gtk,jessevdk/gtk,msteinert/gtk,Sidnioulz/SandboxGtk,jadahl/gtk,Adamovskiy/gtk,Lyude/gtk-,davidgumberg/gtk,jigpu/gtk,ahodesuka/gtk,Distrotech/gtk2,ahodesuka/gtk,Lyude/gtk-,bratsche/gtk-,ahodesuka/gtk,ebassi/gtk,Sidnioulz/SandboxGtk,chergert/gtk,bratsche/gtk-,grubersjoe/adwaita,Distrotech/gtk2,alexlarsson/gtk,Lyude/gtk-,Adamovskiy/gtk,grubersjoe/adwaita,Distrotech/gtk2,Adamovskiy/gtk