Adds a sound frequency controller to glider-instrumentation-sdk.nas,
used for the ilec-sc7. This allows:
- Simpler <sound>.xml files to integrate the glider variometer.
- More accurate frequency scaling (frequency scales exponentially with
vertical speed, so that perceived changes in pitch are linear with
vertical speed).
- Fixes that the variometer sound would not drop at negative vertical
speeds.
All reviewed aircraft now support total energy compensated variometers and
reuse a common implementation. The following issues have been addressed, either
explicitly or as a benefit from the integration:
+ Fixed incorrect variometer readouts at sim/speed-up values != 1
+ Fixed erratic instrument behavior after pause and reinit
+ Reworked all vario needle animations to be smoother.
+ Fixed ASK13 yaw string. Now it deflects to the correct side.
+ Added temperature and (fake) battery readings to ILEC SC7 digital variometer.
+ Fixed ILEC SC7 sign readout (didn't show the minus sign).
Note: The ASK21 models have not been integrated, as they will need a more
profound cockpit overhaul.
