Implemented voice unison mode for 4,6,8 voices.
Added per voice mute, panning, fine tune, env cutoff, env attack, and
env decay.
Added per osc panning, and lfo controlled panning.
Increased length of filter decay env.
Added a 'Voices' tab to Notebook mode and populated the above.
Added UI elements for controlling reverb and struts.  No reverb yet.
Worked around a bug where engine init wasn't running.
Worked around a bug where builds would fail on Ubuntu due to --as-needed
being the default for linker.
Put everything in the right spot, so patch saving/loading works.