_drupento_auth_logout : change cookie host name

In drupal_auth.module, in _drupento_auth_logout function, I think you should use $_SERVER['SERVER_NAME']
instead of $_SERVER['HTTP_HOST']

Because in my case it doesn't work with host like : http://drupal.dev:8080/
$_SERVER['HTTP_HOST'] return drupal.dev:8080
$_SERVER['SERVER_NAME'] return drupal.dev