WHDLoad.hdf updates + warning cleanups

Created by: sonninnos

New features:

• Script called MkCustom for simplest custom file handling. Launches after quitting WHDLoad.
• If .slave is not in the root of the HDF, it will also be searched under the first found directory.
• Saves can be redirected to a separate WHDSaves.hdf. Repo provides an empty 2MiB HDF.
• Both HDF-files can be located either in RA system or saves.

Fixes:

• HDF path can now include ","-character.
• Broader support for different kind of HDFs.
• No more requesters if RA's System volume is not available.
• Disabled directory filesystem completely for Android & Switch.

Closes #191 (closed) Closes #194 (closed)

Bonus:

• Compilation warning cleanups