Fix undefined hasOwnProperty in IE8

IE < 9 does not define `hasOwnProperty` for host objects
(see http://stackoverflow.com/a/8159434). This seems to
have been fixed in systemjs core already (see
systemjs/systemjs@1ee77a).

templates/global-helpers.js

@@ -1,6 +1,6 @@
 (function(__global) {
   var loader = $__System;
-  var hasOwnProperty = __global.hasOwnProperty;
+  var hasOwnProperty = Object.prototype.hasOwnProperty;
   var indexOf = Array.prototype.indexOf || function(item) {
     for (var i = 0, l = this.length; i < l; i++)
       if (this[i] === item)