bugfix: divPoly could produce an 8th point after several calls because some of the old clipPoly code on which it was based
can add the same point twice consecutively (interpolation+adding the point).
Rather than raising the buffer I rewrote divPoly to avoid adding the same point twice.
Merge pull request #15 from axelrodR/master

bugfix: divPoly caused a stack overrun by producing an 8th point