[TASK][DOC] Sample LDAP configuration with ldap.forumsys.com

Change-Id: I4c5cd6adde8b1f3b9c75f65eb0ee9e253e3da573
Reviewed-on: http://review.typo3.org/32173
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>