Revert "io/router: [API] don't emit Enter and Leave events for touch input"

This reverts commit cd0c9dab9f. It turns out
that Enter/Leave is important for cancelling press-then-release-outside
for clickables.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

io/router/pointer.go

@@ -770,7 +770,6 @@ func (q *pointerQueue) deliverEnterLeaveEvents(p *pointerInfo, events *handlerEv
 			p.handlers = append(p.handlers[:0], hits...)
 		}
 	}
-	if e.Source == pointer.Mouse {
 	// Deliver Leave events.
 	for _, k := range p.entered {
 		if _, found := searchTag(hits, k); found {
@@ -797,7 +796,6 @@ func (q *pointerQueue) deliverEnterLeaveEvents(p *pointerInfo, events *handlerEv
 			events.Add(k, e)
 		}
 	}
-	}
 	p.entered = append(p.entered[:0], hits...)
 }