The code disables lookahead between two extruding moves with
significantly different extrude ratios. Unfortunately, it was
possible for very tiny moves to show different extrude ratios just due
to how the slicer implements rounding when it produces the gcode.
Allow lookahead to be enabled between moves with extrude ratios that
are different if they don't noticeably produce more or less extrusion.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
9bf73cd72d