[TASK] DataHandler::getAutoVersionId() should be public

The method getAutoVersionId() in DataHandler/t3lib_TCEmain
should be public. The method is a helper to access the accordant
member variable that get's filled during workspace actions and
thus is useful in hooks as well.

Change-Id: Ie1f55d92b8e72e6ab68a563f0c1c52762239e102
Resolves: #45050
Releases: 6.1, 6.0, 4.7, 4.6, 4.5
Reviewed-on: https://review.typo3.org/17905
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader