Source
FreeGlut doesn't support CGL, so I don't see why they're including the CGL
OpenGL headers.
https://sourceforge.net/p/freeglut/bugs/221
--- include/GL/freeglut_std.h.orig 2014-10-17 09:28:24.000000000 -0700
+++ include/GL/freeglut_std.h 2015-03-27 11:56:29.000000000 -0700
# include <EGL/egl.h>
# include <GLES/gl.h>
# include <GLES2/gl2.h>
-#elif __APPLE__
-# include <OpenGL/gl.h>
-# include <OpenGL/glu.h>
#else
# include <GL/gl.h>
# include <GL/glu.h>