Add VTK_USE_COCOA and VTK_USE_X to VTK config file

When building LookingGlassVTKModule externally (thanks to PR Kitware/LookingGlassVTKModule#9, it fails to include vtkCocoaLookingGlassRenderWindow.mm and vtkCocoaLookingGlassRenderWindow.h (see here and issue KitwareMedical/SlicerLookingGlass#2)

Moving forward, I would like to expose option like VTK_USE_COCOA and VTK_USE_X into a config file.

What is the CMake equivalent of vtkRenderingOpenGLConfigure.h ?