[gtk+] Document GDK_TOUCHPAD_GESTURE_MASK

[Matthias Clasen <matthiasc src gnome org>]

commit 7435c8777568fa57b88c4b20fb4710a3a9fc2bda
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Nov 18 10:21:15 2015 -0500

    Document GDK_TOUCHPAD_GESTURE_MASK

 gdk/gdktypes.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/gdk/gdktypes.h b/gdk/gdktypes.h
index 252922d..bcd499d 100644
--- a/gdk/gdktypes.h
+++ b/gdk/gdktypes.h
@@ -392,6 +392,7 @@ typedef enum
  * @GDK_SCROLL_MASK: receive scroll events
  * @GDK_TOUCH_MASK: receive touch events. Since 3.4
  * @GDK_SMOOTH_SCROLL_MASK: receive smooth scrolling events. Since 3.4
+   @GDK_TOUCHPAD_GESTURE_MASK: receive touchpad gesture events. Since 3.18
  * @GDK_ALL_EVENTS_MASK: the combination of all the above event masks.
  *
  * A set of bit-flags to indicate which events a window is to receive.