Log Message:
fasttracker2: update to b157

Changes since b156

Beta #157 - 27.05.2019
- Fixed: Songs passed to the binary as an argument had to include full path or
  else it would refuse to load.
- Fixed: When loading unsigned 8-bit stereo .WAVs and reading the left or right
  channel only, the very last sample point would be wrong (and cause a click).
- Fixed: Properly clamp Disk Op. filesizes to 2GB on non-Windows systems
- AIFF/WAV sample loading now takes up less RAM during loading. WAV loading is
  also faster, especially when loading 24-bit samples.
- Never attempt to load files bigger than 2GB (not compatible), and also ask
  the user before loading files over 128MB in size, in case it was by accident.
- Allow loading even more broken/quirky .MOD/.FT songs
- Pause audio mixer while hand drawing sample data with the mouse, this is
  needed for safety reasons. (original FT2 does this too)
- Unroll tight sample loops to prevent the audio channel mixer from doing many
  loop wrapping iterations (minor optimization). This is only applied if there
  is no data after the loop end point. Also yes, this is done in real time
  as you modify sample data or load new samples.
- Small code cleanup