Added state[] variable to XFader DSP object.
Completed _cmDspSysPgm_AvailCh() example program.

The phasor value must be limited to a max value - the size of the wave table
otherwise the resolution of the phasor object phase counter eventually
diminishes due to the increasing value of the integer part of the
floating point value.  This will result in distortion in the wave table
output because the phase value will not increment reliably.

useThreadFl allows the background file loading thread to be enabled and disabled.

Added VECT_OP_FUNC()'s MultSumVVS() and SquaredSum().

DSP Wavetable object now transmits 'done' after last sample of the
last loop and provides running output of the current audio file
index via 'fidx'.