[BUGFIX] Assure correct INCLUDE_TYPOSCRIPT with relative paths on subpages

If a subpage has a template that clears the setup, INCLUDE_TYPOSCRIPT
will not work with relative paths anymore. This patch assures that always
the correct file is included.

Change-Id: I43b524c7c0fde7211ccbfc8481e2bbfd00bb4c0e
Resolves: #71197
Releases: master
Reviewed-on: https://review.typo3.org/44432


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>