Calculate the next "cornering" minimum and maximum for each move. The
"cornering minimum" is the lowest speed the head will reach
immediately after this move (with no interleaving acceleration or
cruising). The "cornering maximum" is the maximum speed the head will
reach after the cornering minimum (with no interleaving deceleration
or cruising).
These cornering calculations will be helpful in the extruder "pressure
advance" code.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>