Merged changes in the trunk up to revision 52191.

Conflicts resolved:
source/blender/makesdna/DNA_scene_types.h

release/scripts/startup/bl_operators/presets.py

@@ -554,6 +554,12 @@ class WM_MT_operator_presets(Menu):
 
     def draw(self, context):
         self.operator = context.active_operator.bl_idname
+
+        # dummy 'default' menu item
+        layout = self.layout
+        layout.operator("wm.operator_defaults")
+        layout.seperator()
+
         Menu.draw_preset(self, context)
 
     @property