boxpointer: Disable offscreen redirect for popup menus
The ClutterOffscreenEffect has a weird bug that lately appears very often in multi monitor setups, this bug causes the culling checks to return that the actor isn't on stage and therefore shouldn't be painted.
This obviously causes visual issues and can lead to the popup menus being completely unusable. To work around this bug until the root cause is found, disable the offscreen effect for popup menus for now.
Fixes #1049 (closed)