Get rid of strange code: preliminary check of self-intersections is made on a polygonal representation of a curve, it is able to find possible intersections, but after that it filter out segments neighbor to the pair of non-intersected segments.
Test case de step_4 I1 has been marked BAD, because the self-intersection is treated correctly, but the projection algorithm generates such crooked 2D curve.
Reference data in test cases heal split_angle_advanced ZA5 and ZA6 has been updated, because those shapes have self-intersected edges, which are being detected now.
