Got ACL scope logic working again and began enforcing it. Breaking API change: assigning page title with $template->tpl_strings['PAGE_NAME'] will no longer work, use $template->assign_vars(). Workaround may be added later. Test for assign_vars method if compatibility needed. Added namespace processor API (non-breaking change). Several other things tweaked around as well.
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>blank_page</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<script type="text/javascript">
parent.TemplateDialog.loadCSSFiles(document);
</script>
</head>
<body id="mceTemplatePreview" class="mceContentBody">
</body>
</html>