Log Message:
audio/fasttracker2: Updates to v1.21

Changes since v1.20:

v1.21 - 22.04.2020
- macOS/Linux: The initial working directory would not get properly set when
  opening Disk Op.
- Bugfix: The custom directory paths in the config could contain unwanted junk
  at the end if the loaded config file was saved from real FT2.
- Bugfix: If you were skilled enough to beat the very last Nibbles level, your
  potential entry in the highscore table would show garbled level graphics.
- Show a warning if either of the Buttons/Desktop palette colors are so dark
  that you might have issues seeing the walls in Nibbles.
- "Space Pigs" palette replaced with a new (low contrast) "Dark \ 
mode" palette
- Some more small miscellaneous fixes not worth of a mention