Pour MAC glu.h est dans OpenGL

#  ifdef __APPLE__
#    include <OpenGL/glu.h>
#  else
#    include <GL/glu.h>
#  endif

Code/Visu/otbImageWidgetPolygonForm.h

@@ -23,9 +23,9 @@
 #include "otbImageWidgetFormBase.h"
 #include "otbPolygon.h"
 #  ifdef __APPLE__
-#    include <OpenGL/gl.h>
+#    include <OpenGL/glu.h>
 #  else
-#    include <GL/gl.h>
+#    include <GL/glu.h>
 #  endif
 
 namespace otb