[TASK] Fix autologin for TYPO3 >= 6.2.5

Due to a change in core the session cookie isn't always set.

This patch adds a dummy value to the user session that forces
the creation of the fe_user cookie that is needed to keep login active.

Change-Id: I9e38202162b0096c43f487a4a4d3657764a430eb
Reviewed-on: http://review.typo3.org/33978
Reviewed-by: Sebastian Fischer <typo3@evoweb.de>
Tested-by: Sebastian Fischer <typo3@evoweb.de>