add VCD dump for waveform viewing

[philburk]

This would involve storing all important timing information in a compact format.
It can be dumped to a VCD format file and viewed using a VCD waveform viewer.
Store:
task awake/asleep
buffer depth
cpu index

Dump:
synthesized ideal burst timing so we can see when a task is late

[philburk]

Also show:

• number of voices
• note on/off
• buffer size