regression: OpenGL2 backend broke support for LineStipple

This issue was created automatically from an original Mantis Issue. Further discussion may take place here.

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The VTK 6.3 OpenGL2 backend does not support the vtkProperty::SetLineStipplePattern() public API.

This is due to line stipple being removed from OpenGL version 3.1.

For us, this is an important regression in functionality, because we use line stipple in many places.