Drop unimplemented functions
Drop unimplemented functions

These were added to the header by mistake in a recent commit.
They have no implementation, so dropping them won't cause
any harm.

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