[vtkusers] opengl support

[Bruno Arbter]

Hi everybody,

I'm using qt with vtk (QVTKWidget). Testing the QVTKWidget on OpenGL support
with QVTKWidget::SupportsOpenGL(), I wondered that the result was 0 (false)
even if the result looks fine. Same happens when testing the Medical1
example (without qt support). I already checked the OpenGL requirements from
FAQ, they are fullfilled.

Any idea? Is OpenGL used anyway?

Thanks
Bruno