Replace goog.events.Event/EventTarget system with our own

This also removes goog.events.listen, goog.events.unlisten,
goog.events.unlistenByKey and goog.events.BrowserEvent.

src/ol/interaction/dragrotateinteraction.js

@@ -112,8 +112,8 @@ ol.interaction.DragRotate.handleDownEvent_ = function(mapBrowserEvent) {
     return false;
   }
 
-  var browserEvent = mapBrowserEvent.browserEvent;
-  if (browserEvent.isMouseActionButton() && this.condition_(mapBrowserEvent)) {
+  if (ol.events.condition.mouseActionButton(mapBrowserEvent) &&
+      this.condition_(mapBrowserEvent)) {
     var map = mapBrowserEvent.map;
     map.getView().setHint(ol.ViewHint.INTERACTING, 1);
     map.render();