Update Smarty to 3.1.21

- add missing block.tphp, block.textformat.php, function.popup.php,
  function.popup_init.php
- update function in function.html_checkboxes.php,
  function.html_options.php

www/Smarty-3.1.21/plugins/modifiercompiler.string_format.php

@@ -0,0 +1,25 @@
+<?php
+/**
+ * Smarty plugin
+ *
+ * @package    Smarty
+ * @subpackage PluginsModifierCompiler
+ */
+
+/**
+ * Smarty string_format modifier plugin
+ * Type:     modifier<br>
+ * Name:     string_format<br>
+ * Purpose:  format strings via sprintf
+ *
+ * @link   http://www.smarty.net/manual/en/language.modifier.string.format.php string_format (Smarty online manual)
+ * @author Uwe Tews
+ *
+ * @param array $params parameters
+ *
+ * @return string with compiled code
+ */
+function smarty_modifiercompiler_string_format($params)
+{
+    return 'sprintf(' . $params[1] . ',' . $params[0] . ')';
+}