Log Message:
audio/fasttracker2: Updates to v1.20

Changes since v1.19:

v1.20 - 13.04.2020
- x86_64/amd64 users now get 32.32 fixed-point precision in the audio channel
  mixer, an extra 192kHz mixing frequency mode (may only work with a larger
  buffer size), and double the amount of phases in the cubic spline table. This
  will only make an improved outcome in very few cases (like extremely high/low
  channel rates), so don't expect to hear any difference. Non-x86_64 users now
  lose 96kHz mode as it was a bit unsuitable with 16.16 fixed-point precision.
- The "Volume" function in Smp. Ed. now has more precision and takes \ 
less time
  to complete. Not that it was slow to begin with...
- Increased the minimum .WAV rendering frequency from 8kHz to 44.1kHz, because
  the mixer delta calculations could overflow on such low rates.
- Some more small miscellaneous changes not worth of a mention
- Code cleanup