Rename ol.Observable#dispatchChangeEvent() to #changed()

Since dispatchChangeEvent does not only dispatch a change event, but
also increases the revision counter, the method name should reflect
this.

src/ol/geolocation.js

@@ -173,7 +173,7 @@ ol.Geolocation.prototype.positionChange_ = function(position) {
       ol.sphere.WGS84, this.position_, coords.accuracy);
   geometry.applyTransform(this.transform_);
   this.set(ol.GeolocationProperty.ACCURACY_GEOMETRY, geometry);
-  this.dispatchChangeEvent();
+  this.changed();
 };