Really, really logout (fixes r2467).

index.php

@@ -97,7 +97,7 @@ if ($RCMAIL->action=='login' && $RCMAIL->task=='mail') {
   else if ($_SESSION['temp'] && !empty($auth['user']) && !empty($auth['host']) && isset($auth['pass']) && 
             $RCMAIL->login($auth['user'], $auth['pass'], $auth['host'])) {
     // create new session ID
-    unset($_SESSION['temp']);
+    rcube_sess_unset('temp');
     rcube_sess_regenerate_id();
 
     // send auth cookie if necessary

program/include/rcmail.php

@@ -793,6 +793,8 @@ class rcmail
    */
   public function kill_session()
   {
+    foreach (array_keys($_SESSION) as $var)
+      rcube_sess_unset($var);
     $_SESSION = array('language' => $this->user->language, 'auth_time' => time(), 'temp' => true);
     rcmail::setcookie('sessauth', '-del-', time() - 60);
     $this->user->reset();