Make sure that jQuery is being exposed outside of core (this will be stripped...

Make sure that jQuery is being exposed outside of core (this will be stripped during the build process). Follow-up to #7011.

src/core.js

-(function() {
+var jQuery = (function() {
 
 // Define a local copy of jQuery
 var jQuery = function( selector, context ) {
@@ -826,6 +826,6 @@ function doScrollCheck() {
 }
 
 // Expose jQuery to the global object
-window.jQuery = window.$ = jQuery;
+return window.jQuery = window.$ = jQuery;
 
 })();