glext

Former-commit-id: 7a24f9f786e0a11f6702724db411cedc1ecb67be

include/igl/OpenGL_convenience.h

@@ -18,6 +18,7 @@
 #if __APPLE__
 #  include <OpenGL/gl.h>
 #  include <OpenGL/glu.h>
+#  include <OpenGL/glext.h>
 #elif defined(_WIN32)
 #    define NOMINMAX
 #    include <Windows.h>