textview: Set up controllers on the GTK_PHASE_TARGET propagation phase
textview: Set up controllers on the GTK_PHASE_TARGET propagation phase

This way events are managed by gestures in the event handlers themselves,
respecting the execution order already assumed by subclasses around.

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