Use extend rather than prototype for createFrame

Using prototype has a large performance impact for the common case of a
sparse set of private variable data points. Rather than incurring the
overhead of creating and walking the prototype tree for this, performing
an extend by copy.

lib/handlebars/base.js

@@ -73,10 +73,9 @@ Handlebars.registerHelper('blockHelperMissing', function(context, options) {
 
 Handlebars.K = function() {};
 
-Handlebars.createFrame = Object.create || function(object) {
-  Handlebars.K.prototype = object;
-  var obj = new Handlebars.K();
-  Handlebars.K.prototype = null;
+Handlebars.createFrame = function(object) {
+  var obj = {};
+  Handlebars.Utils.extend(obj, object);
   return obj;
 };