vtkRenderingExternal: Fixed camera setup for Vive HMD using VruiVTK.
Camera position and focal point are wrong which popped up by using the vtkRenderingExternal
-module with VruiVTKs VolumeViewer in combination with HTC Vive HMD. Maybe it was introduced by copy and paste from Rendering/Core/vtkCamera.cxx. See this VruiVTK issue for more details.