Now supports stereo tracks. Several tweaks to error messages,
validation logic, and accuracy improvements.
Includes a fix for summary64K (incorrect rms drawn on zoomed
out waveform).
... Should have no effect on generated code, except perhaps some slight faster
virtual function calls. Mostly useful as documentation of design intent.
Tried to mark every one of our classes that inherits from another, or is a
base for others, or has abstract virtual functions, and a few others besides.