checkshape ignores self-intersection of wires in specific case

1. if two edges from being researched wire have one common vertex.

2. These edges intersect each other in some point.

3. deviation from each edge to line connecting intersect point with "common vertex" point isn't greater than double tolerance of participating edge

this intersect point is ignored by checkshape (due to, i suppose, checkshape determines this intersection as the beginning of the "topological" segment of intersection with its end in common vertex).