Fix the polygon touching contour test in poly_ChkContour

Fix the polygon touching contour test in poly_ChkContour

The following test-cases were used to help verify the changes:

This polygon forms a self-touching shape like this:

\|  However, the right-hand edge does NOT have a node at the junction.
/|  This previously caused it to fail the self-intersection test.
    It should be reported as good.

Polygon("")
  (
    [85000 50000] [85000 90000] [83000 90000]
    [83536 63535] [85000 59999] [83535 56464]
  )

This polygon forms a self-intersecting shape like this:

 |/  (The vertical section is a straight line with no node in the middle)
/|   It must be reported as bad.

Polygon("")
  (
    [85000 50000] [85000 90000] [83000 90000]
    [83536 63535] [85000 59999] [89535 56464]
  )

This polygon self-intersects, and must be reported as bad:

Polygon("")
  (
    [160000  50000] [160000  90000] [170000 100000]
    [180000 120000] [180000 150000] [160000 150000]
    [160000 120000] [170000 100000] [180000  90000]
    [180000  50000]
  )

This polygon self-touches, and should be reported as good:

Polygon("clearpoly")
  (
    [120000  50000] [120000  90000] [130000 100000]
    [120000 120000] [120000 150000] [140000 150000]
    [140000 120000] [130000 100000] [140000  90000]
    [140000  50000]
  )