Gobble "spurious" EnterNotify events when moving an appIcon or a dock
This is a bug fix. Bug overview: if an AppIcon is moved rapidly over a Clip
set to auto-expand, the latter may erroneously auto-expand afterwards.
How to reproduce it: set a Clip to auto-collapse, and make sure it contains a
(random) AppIcon, so as to easily visualise its open/close state. Now move
rapidly an AppIcon over the Clip. Try to move it so fast that the cursor
sometimes is out of the AppIcon's tile. Then, replace the AppIcon out of the
Clip.
Explanation and correction: if, while the AppIcon was being moved, the mouse
cursor entered at least once in the Clip's tile, the latter is going to
receive an EnterNotify event (after the AppIcon is replaced) and thus expand
automatically after the relevant delay. The solution is to simply "gobble"
(i.e., ignore) all EnterNotify events when moving an AppIcon.