Preserve an A-Z => a-z filename tolerance for case-sensitive filesystems

[dwatteau]

ScummRp::_gameDef contains a list of expected filenames, in order to use the right data to translate each game.

They were mostly DOS games, so the filenames in the table are all in uppercase. That's still fine today for (nearly) all Windows and macOS setups, because they still use a case-insensitive filesystem today.

But it's still possible to have a case-sensitive filesystem on them, and that's the default on most other systems (e.g. Linux, BSDs…).

The current workaround is just to have your local files named in DOS mode, that is all in uppercase. Maybe it would just be simpler if it remains this way.

But it might be convenient if our tools tolerated an A-Z => a-z substitution (only for game data filenames, and only for ASCII letters). ScummVM does this, too.

It should remain simple, though. We don't want the tools to do dozens and dozens of checks just for this.