Add a prototype from MDN for indexOf to be used in browsers where it is not supported.

include/util.js

@@ -57,6 +57,34 @@ if (!Array.prototype.map)
   };
 }
 
+// IE <9 does not support indexOf
+//This prototype is provided by the Mozilla foundation and
+//is distributed under the MIT license.
+//http://www.ibiblio.org/pub/Linux/LICENSES/mit.license
+if (!Array.prototype.indexOf)
+{
+  Array.prototype.indexOf = function(elt /*, from*/)
+  {
+    var len = this.length >>> 0;
+
+    var from = Number(arguments[1]) || 0;
+    from = (from < 0)
+         ? Math.ceil(from)
+         : Math.floor(from);
+    if (from < 0)
+      from += len;
+
+    for (; from < len; from++)
+    {
+      if (from in this &&
+          this[from] === elt)
+        return from;
+    }
+    return -1;
+  };
+}
+
+
 // 
 // requestAnimationFrame shim with setTimeout fallback
 //