Make :undo a bit saner. Add TODO about config.name checks.

common/content/mappings.js

@@ -50,6 +50,8 @@ the terms of any one of the MPL, the GPL or the LGPL.
  */
 function Map(modes, keys, description, action, extraInfo) //{{{
 {
+    modes = Array.concat(modes);
+
     if (!extraInfo)
         extraInfo = {};