[BUGFIX] Extension Scanner finds files on Windows

The extension scanner now also works on windows, as
the paths have been fixed to contain only one type of
slashes.

Change-Id: I9859f28029931f19f06873145e1de572fbb8bdfa
Resolves: #82153
Releases: master
Reviewed-on: https://review.typo3.org/53763


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>