I.e., when acceleration * steps per mm > 2,000,000.
This was done by changing MultiU24X24toH16 to take a 32b bit operand.
Removed the claim that stepper.cpp uses the Leib algorithm.
HOME_POS is now always where the endstop is and can be outside the limits.
The limits are now defined by MIN_POS and MAX_POS rather than HOME_POS and MAX_LENGTH.
The Z is axis now homed first if direction is away from the bed.
Saguinololu limit pins change from MIN to MAX according to the homing direction.
Chris Palmer
