Fix some non-jQuery DOM manipulations and change height
calculation to make scrolling by cursor working again.

Resolves: #68442
Releases: master
Change-Id: Ifcac7b25ee8a11797e5cc5c2639c9987c9a5efd2
Reviewed-on: http://review.typo3.org/41829


Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>