[CRUSH-build] remapping the joysticks

[Bill Bennett]

Joe and I looked at the behavior of the two joysticks and they are close to 
identical. It's a little hard to be completely objective about this, since 
what we're trying to do is guage whether the stick output is the same for 
identical hand-driven inputs. But they're quite close. So I don't think 
that's the cause of the pulling. Seems more likely it's a motor issue, or 
chains tighter on one side, or something like that.

The other thing we might want to do is put a curve on the joysticks when 
used in 2 stick mode that gives the driver better control at low speed. I 
think a input to output mapping that's a simple 3 segment linear map would 
be fine. The three segments would be (relative to joystick center):
- zero output up to y1 (the dead zone)
- a segment from y1 to y2 at slope s1 - use a low slope for good control at 
low speeds
- a third segment from y2 to ymax at slope s2 - use a higher slope at high 
speeds, less fine control needed

I started working on this with Joe last night, then MPLAB choked and threw 
away the changes. It was not much work, we can restart it today.

Bill