unwieldytracker clvnmix

changes from the original utrk sources:

apr 2009: something to do with being able to show the "about" box without crashing or hanging

nov 2011: fixed clicks in the 24 bit stereo sample interpolator (thx to ld0d)

feb 2012: removed polac out support, implemented native multi io (utrk2)
16 stereo output channels are always available. all tracks send their output to the first channel by default.
use effect "78 000n", where n = 0..F to select an output channel for that track.

