send REMOTE_ADDR to IMAP and SMTP

[lacri]

The German BNA (Bundesnetzagentur)  requires that the IP from the user is submitted to the IMAP server for monitoring.
 Here is a small workaround for this.

Add in rcube_imap_generic.php by the function login($user, $password)

after this line list($code, $response) = $this->execute('LOGIN', array(
            $this->escape($user), $this->escape($password)), self::COMMAND_CAPABILITY);
this execute command// send remote_address to imap
                $this->execute('NOOP', array($this->escape($_SERVER['REMOTE_ADDR'])));
For SMTP, the specification of the BNA can be achieved with the additional_message_headers plugin.