add an XXX note for the 3.16.0 release

www/common/sframe-common.js

@@ -630,6 +630,7 @@ define([
             });
 
             ctx.sframeChan.on('EV_NEW_VERSION', function () {
+                // XXX lock the UI and do the same in non-framework apps
                 var $err = $('<div>').append(Messages.newVersionError);
                 $err.find('a').click(function () {
                     funcs.gotoURL();