Fix non Delaunay internal edges added by RecoverEdge().

During RecoverEdge() process, some edges are introduced by
the call to vtkPolygon::Triangulation which do not care about
Delone's criterion.
This fix check the new internal edges (not on the boundary
of the tessellated polygons) and flip them if necessary.
It fixes the issue reported here:
http://www.vtk.org/Wiki/images/2/26/IncorrectCDT.png

Change-Id: I6ec482bcb8e6c8014909c1e8a16b4596180149d3
Merge topic 'Fix-vtkDelaunay2D-CDT-RecoverEdge' into master

85e985ef Fix non Delaunay internal edges added by RecoverEdge().