widget: Add checks for setting state flags
widget: Add checks for setting state flags

This is more for GTK developers to catch when they forgot to change
GTK_STATE_FLAGS_BITS after adding a new state flag than to prevent
widget developers from using the wrong flags.

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