Change in handling of frameoffset for multistreamed instruments and sampletracks.
- Instead of holding the offset for the lifetime of the playhandle, negate the offset in the first period
- Multistream-instruments require some small changes: they have to now check for the offset and accordingly leave empty space in the start of the period (already done in this commit)
- There are possibly optimizations that can be done later
- This change is necessary so that we can have sample-exact models, and sample-exact vol/pan knobs for all instruments. Earlier multistream instruments were always rendering some frames ahead-of-time, so applying sample-exact data for them would have been impossible, since we don't have the future-values yet...
Instead of having various flags for realizing the arpeggion functionality
use a more generic approach here using the recently introduced "origin"
property.
The volume of an InstrumentTrack is applied separately when post-processing
the audio buffer and is not related to MIDI processing. It therefore should
not be included into MIDI velocity calculation.
Closes#301.
Next big coding style update - this time all PlayHandle classes are
affected. Functions like done() and released() were renamed to
isFinished() and isReleased().
