DoctrineBundle 1.3 (compatible with Symfony 2.3+) added the possibility to configure the server_version option of DBAL 2.5.
This option needs to be documented because Doctrine ORM unfortunately triggers the retrieval of the database platform too early currently, and for drivers needing to change the platform based on the server version, this triggers an early connection to the DB in case it relies on guessing.
This is likely to concern lots of people upgrading to the new DBAL 2.5 given that MySQL is one of the platforms needing version switches

Seedoctrine/DoctrineBundle#351 (comment) for a config example.