The existing junction algorithm limits the speed between two moves by
determining the maximum speed an arc between those two moves would
have if the cetripetal acceleration of that arc did not exceed the
printer's maximum acceleration.
However, should the slicer send an actual arc to the printer, then the
existing junction algorithm would not impose any significant limit on
the travel speed of that arc. This would permit the head to travel in
a circle at high velocity and with a greater centripetal acceleration
than the printer's maximum acceleration. To avoid this, impose a
limit on the junction velocity of short moves so that an approximate
centripetal acceleration of that move does not exceed the move's
acceleration limit.
Suggested by Michael Barbour.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>