gtk: Add GtkEventControllerKey

This event controller is meant to replace usage from key-press/release-event
handlers all through. Optionally it can be set a GtkIMContext, so interaction
is carried by the controller.

po/POTFILES.in

@@ -142,6 +142,9 @@ gtk/gtkentry.c
 gtk/gtkentrycompletion.c
 gtk/gtkeventbox.c
 gtk/gtkeventcontroller.c
+gtk/gtkeventcontrollerkey.c
+gtk/gtkeventcontrollermotion.c
+gtk/gtkeventcontrollerscroll.c
 gtk/gtkexpander.c
 gtk/gtkfilechooserbutton.c
 gtk/gtkfilechooser.c