MDL-27982 remove unsigned support from all UIs and APIs, keep only public API for BC

lib/filterlib.php

@@ -855,6 +855,7 @@ function filter_get_active_in_context($context) {
          ) active
          LEFT JOIN {filter_config} fc ON fc.filter = active.filter AND fc.contextid = $context->id
          ORDER BY active.sortorder";
+    //TODO: remove sql_cast_2signed() once we do not support upgrade from Moodle 2.2
     $rs = $DB->get_recordset_sql($sql);
 
     // Masssage the data into the specified format to return.