[BUGFIX] UpgradeAnalysis fails on symlinked core

Class DocumentationFile compared a real path with
a symlinked path resulting in an exception, even
though both paths are the same.

Now realpath is called for both paths.

Change-Id: Ib1baf8a721ee2bafbba4b4bdeaefc996fdc9a6a8
Resolves: #79690
Releases: master
Reviewed-on: https://review.typo3.org/51586


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Tobi Kretschmann <tobi@tobishome.de>
Tested-by: Tobi Kretschmann <tobi@tobishome.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Josef Glatz <josef.glatz@typo3.org>
Tested-by: Josef Glatz <josef.glatz@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>