move Event.stop function into deprecated.js

lib/deprecated.js

@@ -1041,6 +1041,14 @@ if (!Function.prototype.bindAsEventListener) {
     };
 }
 
+// FIXME: Remove this in 3.0. In 3.0, Event.stop will no longer be provided
+// by OpenLayers.
+if (window.Event) {
+    OpenLayers.Util.applyDefaults(window.Event, OpenLayers.Event);
+} else {
+    var Event = OpenLayers.Event;
+}
+
 /**
  * Class: OpenLayers.Control.MouseDefaults
  * This class is DEPRECATED in 2.4 and will be removed by 3.0.