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