ERR: Still need to define OPENGL_INCLUDE_PATH in addition to the standard OPENGL_INCLUDE_DIR for backward compatability.

Modules/FindOpenGL.cmake

@@ -136,4 +136,7 @@ IF(OPENGL_INCLUDE_DIR)
     SET (OPENGL_INCLUDE_PATH ${OPENGL_INCLUDE_DIR})
 
   ENDIF(OPENGL_gl_LIBRARY)
+
+  SET(OPENGL_INCLUDE_PATH ${OPENGL_INCLUDE_DIR})
+
 ENDIF(OPENGL_INCLUDE_DIR)