Add deprecated doctag for current methods

lib/Cake/Controller/Component/SessionComponent.php

@@ -133,6 +133,7 @@ class SessionComponent extends Component {
  * @param string $key Message key, default is 'flash'
  * @return void
  * @link http://book.cakephp.org/2.0/en/core-libraries/components/sessions.html#creating-notification-messages
+ * @deprecated 3.0.0 Since 2.7, use the FlashComponent instead.
  */
 	public function setFlash($message, $element = 'default', $params = array(), $key = 'flash') {
 		CakeSession::write('Message.' . $key, compact('message', 'element', 'params'));

lib/Cake/View/Helper/SessionHelper.php

@@ -126,6 +126,7 @@ class SessionHelper extends AppHelper {
  *    Supports the 'params', and 'element' keys that are used in the helper.
  * @return string
  * @link http://book.cakephp.org/2.0/en/core-libraries/helpers/session.html#SessionHelper::flash
+ * @deprecated 3.0.0 Since 2.7, use FlashHelper::render() instead.
  */
 	public function flash($key = 'flash', $attrs = array()) {
 		$out = false;