[RELEASE] Release of TYPO3 4.7.20

Change-Id: Ie1c239fcb723c4ecaa1743f6601a4f739f972bd8
Reviewed-on: http://review.typo3.org/33463
Reviewed-by: TYPO3 Release Team <typo3v4@typo3.org>
Tested-by: TYPO3 Release Team <typo3v4@typo3.org>