The GLEW library is optional, but without it you cannot do OpenGL
interop. The hello_world example uses OpenGL interop, but did not check
that GLEW was available. It tried to use GLEW and an error occured.
For header files, this only adds the file to IDE file lists, which is
convenient but not critical. However, the test did find a ligit error in
the hello_world example where the TBB build was actually using the
serial device adapter.
This is needed as it allows the policies specified in the root of
vtk-m to propagate properly to the examples. When CMake
sees a cmake_minimum_required command it resets all policy flags.
Based on the work of Tyson Neuroth and Huu Tan Nguyen at the VTK-m code
sprint.
Shows how to invoke a simple worklet to generate coordinates and colors,
and than use opengl interop to display it to the screen.
