RTS: Add Daniel Sigg's new duotone crossing-time calc.
The new calc has a second order correction.
Add floating point channel for DAC duotone.
New version of duotime() is written by Daniel Sigg.
Improve duotone sample window: old window was centered around - 1/2 cycle. New window is centered around + 1/2 cycle for timing cards with 7 usec duotone crossing, and at 0 cycle for timing cards with 0 usec duotone crossing (as with the latest LPTC firmware version).
Edited by Erik von Reis