Fixing the extend method to work on IE.

In IE, events don't have a `hasOwnProperty` method.  Instead of trusting that the source objects have this method, we call the same on the Object prototype.  If we want to be safer about the `hasOwnProperty` calling done in e3cc96dbfb, we could create an `OpenLayers.Object.has` method that also used the Object prototype.

lib/OpenLayers/BaseTypes/Class.js

@@ -91,7 +91,7 @@ OpenLayers.Util.extend = function(destination, source) {
     destination = destination || {};
     if (source) {
         for (var property in source) {
-            if (source.hasOwnProperty(property)) {
+            if (Object.prototype.hasOwnProperty.call(source, property)) {
                 var value = source[property];
                 if (value !== undefined) {
                     destination[property] = value;