[grits] Fix compiler warning with gluTessCallback

[Andy Spencer <andys src gnome org>]

commit 3cffa87da6bc184f180365787500c0e2e8a418a3
Author: Andy Spencer <andy753421 gmail com>
Date:   Fri Sep 9 06:07:29 2011 +0000

    Fix compiler warning with gluTessCallback

 src/objects/grits-poly.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/src/objects/grits-poly.c b/src/objects/grits-poly.c
index 865d288..67e39e5 100644
--- a/src/objects/grits-poly.c
+++ b/src/objects/grits-poly.c
@@ -34,9 +34,9 @@ static void grits_poly_tess(gdouble (**points)[3])
 
 	/* Tesselate */
 	GLUtesselator *tess = gluNewTess();
-	gluTessCallback(tess, GLU_TESS_BEGIN,  glBegin);
-	gluTessCallback(tess, GLU_TESS_VERTEX, glVertex3dv);
-	gluTessCallback(tess, GLU_TESS_END,    glEnd);
+	gluTessCallback(tess, GLU_TESS_BEGIN,  (_GLUfuncptr)glBegin);
+	gluTessCallback(tess, GLU_TESS_VERTEX, (_GLUfuncptr)glVertex3dv);
+	gluTessCallback(tess, GLU_TESS_END,    (_GLUfuncptr)glEnd);
 	gluTessBeginPolygon(tess, NULL);
 	for (int pi = 0; points[pi]; pi++) {
 		gluTessBeginContour(tess);