QMenu: Sloppy menu selection should allow hovering separators

QMenu: Sloppy menu selection should allow hovering separators

Setting the current action to 0 clears the sloppy region and
closes the submenu if we hover a separator on the way to the
submenu popup. Now, we choose not to while the sloppy delay
timer is running.

This is a backport of I9d1b1358fe64c259dc47f35db8fc8f2b19a73153
from qt/qtbase.

Task-number: QTBUG-20094
Change-Id: If4b3cff05a9bcb41cee3e49490d4cc5fc3595821
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>