[BUGFIX] Fix multiple "Quit without saving?" messages

In some cases, the event handler was bind multiple times.
This patch moves the binding into a new place.

Resolves: #68095
Releases: master
Change-Id: I40aeb1305b6e0c061a202ddb31a9e8f9fc9b9630
Reviewed-on: http://review.typo3.org/41160


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>