API: Decouple GdkWindow from GdkDrawable
API: Decouple GdkWindow from GdkDrawable

Make GdkWindow no longer typedeffed to GdkDrawable, but instead make it
be its own (private) type.

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