This commit will help implementing click actions triggered by pointerup
behind a FF.

In 'listenActionEvents', we expect that a 'click' event is preceded by
a single 'pointerdown' event. It turns out this is not always the case
on multitouch devices.

This issue would be amplified when listening to 'pointerup' events.

Let's just focus on the 'primary' pointer events. This will ignore
secondary touches until we implement proper support for them (if ever).

This slightly change the action beginning, but takes any activity
produced by 'pointerup' 'mouseup' 'touchend' events into account. If
those actions don't produce any activity, the action start is likely to
be the same as before, since 'pointerup/mouseup/touchend' should be
triggered very close to the 'click' event.

…gnals--track-pointerup