This variable was introduced before version 1.8 - I am using it in 1.7.1 currently.
Permanently deleting files? 
Sorry if this should be obvious, but is there a good way to permanently delete a file in >1.11? I tried changing wgFileStore['deleted']['directory'] to /dev/null and it didn't like that much. Thanks!
- About the only that I have found so far to do is either manually or via a cron script run the deleteArchivedFiles.php in the maintenance directory.