before sending a B_MOUSE_DOWN message to any other view. This fixes bug
594 for real and another bug in BMenuBar. BMenuBar tracking will also
be simplified a bit because of this. Install items to a NULL window on
Show() as does R5 (although I don't know why yet).
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@17605 a95241bf-73f2-0310-859d-f6bbb57e9c96