[BrowserKit] added missing @return PHPDoc for the Client::submit() method.

src/Symfony/Component/BrowserKit/Client.php

@@ -214,6 +214,8 @@ abstract class Client
      * @param Form  $form   A Form instance
      * @param array $values An array of form field values
      *
+     * @return Crawler
+     *
      * @api
      */
     public function submit(Form $form, array $values = array())