colorplane: Fully port to GtkGesture
colorplane: Fully port to GtkGesture

A GtkGestureDrag is used for color selection, removing also the
need to track the pointer state in widget data. The GDK grab performed
just to set the crosshair cursor has been replaced by a call
to gdk_window_set_device_cursor(), which will be unset if the
drag operation is finished, or cancelled due to the implicit grab
being broken.

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