[TASK] require-statements should use absolute paths

require-statements relying on the current working-
directory and/or a certain include-path setting
can cause unexpected behaviour.
A path is added for those cases. For the current
working-directory simply using __DIR__ is okay.

Change-Id: I959c8f4a1d25ca1403e7dcecb0bc20826c7c5059
Resolves: #49991
Releases: 6.2
Reviewed-on: https://review.typo3.org/22270
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring