skins2: For Linux, correct files that cannot be loaded because of a workaround that only makes sense on Windows.

Forcefully setting a file name with lower case was inserted to solve an issue that is only true on Windows. On Linux, upper/lower case must not be tampered with.
This resulted in skins like Orangeade.vlt failing to load their fonts on Linux.
(cherry picked from commit 4f1060a7)