fix typedef problem found with MSDev 6.0
diff --git a/include/GL/glu.h b/include/GL/glu.h
index 0327ac2..36bd7c1 100644
--- a/include/GL/glu.h
+++ b/include/GL/glu.h
@@ -250,10 +250,10 @@
typedef struct GLUtesselator GLUtesselator;
#endif
-typedef struct GLUnurbs GLUnurbsObj;
-typedef struct GLUquadric GLUquadricObj;
-typedef struct GLUtesselator GLUtesselatorObj;
-typedef struct GLUtesselator GLUtriangulatorObj;
+typedef GLUnurbs GLUnurbsObj;
+typedef GLUquadric GLUquadricObj;
+typedef GLUtesselator GLUtesselatorObj;
+typedef GLUtesselator GLUtriangulatorObj;
#define GLU_TESS_MAX_COORD 1.0e150