[BUGFIX] Sorting files in filelist is case sentive

The sorting for files in the filelist is case sensitive while the sorting
for folders is not. The sorting should be adjusted to be identical for
files and folders.

Change-Id: I2aee28f42beb1f9b4b1eb969ee5503fd9bea0e23
Fixes: #46541
Releases: 6.1, 6.0
Reviewed-on: https://review.typo3.org/19189
Reviewed-by: Benjamin Mack
Tested-by: Benjamin Mack