title.gettext deletion performed only by list owners, need authentication

is_owner([listname],[sender])  smtp       -> request_auth
is_listmaster([sender])        smtp       -> request_auth
is_owner([listname],[sender]) md5,smime -> do_it
is_listmaster([sender])       md5,smime -> do_it
true()                        smtp,md5,smime -> reject(reason='del_owner')
