We previously included windows.h in numerous locations using different
techniques to guard against bringing in parts of the file that are bad
(min/max macros, etc). This solves the problem by consistently using
vtkm/internal/Windows.h to setup everything.
Specifically, I am trying to compile the code on OSX. OSX uses OpenGL
libraries in a different directory than most other installs (including
X11) and does not generally support GLX. These changes remove the files
that support GLX in systems that do not support it.
I also added several header files to the CMake lists that were not there
but should have been.
