Adding a pinch handler for multi-touch devices. Great patch from Bruno. p=bbinet, r=me (closes #3077)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@11389 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Events.js

@@ -104,6 +104,20 @@ OpenLayers.Event = {
         return event.touches && event.touches.length == 1;
     },
 
+    /**
+     * Method: isMultiTouch
+     * Determine whether event was caused by a multi touch
+     *
+     * Parameters:
+     * event - {Event}
+     *
+     * Returns:
+     * {Boolean}
+     */
+    isMultiTouch: function(event) {
+        return event.touches && event.touches.length > 1;
+    },
+
     /**
      * Method: isLeftClick
      * Determine whether event was caused by a left click.