[FOLLOWUP][TASK] Introduce getters for $GLOBALS in ext:setup

Resolves: #65372
Releases: master
Change-Id: I19d67cb8de220f25f74667bc39a5ca25c62c9500
Reviewed-on: http://review.typo3.org/37309


Reviewed-by: Alexander Opitz <opitz.alexander@googlemail.com>
Tested-by: Alexander Opitz <opitz.alexander@googlemail.com>
Reviewed-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Andreas Fernandez <andreas.fernandez@aspedia.de>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>