window: Keep track of popover children mapped status
window: Keep track of popover children mapped status

In order to maintain visibility of the GdkWindow that's the parent window
of the popover widget.

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