Fix MDR surface indexes overflow check

Also, use the check overflow macro like everywhere else.

code/renderergl1/tr_animation.c

@@ -346,7 +346,7 @@ void RB_MDRSurfaceAnim( mdrSurface_t *surface )
 	oldFrame = (mdrFrame_t *)((byte *)header + header->ofsFrames +
 		backEnd.currentEntity->e.oldframe * frameSize );
 
-	RB_CheckOverflow( surface->numVerts, surface->numTriangles );
+	RB_CHECKOVERFLOW( surface->numVerts, surface->numTriangles * 3 );
 
 	triangles	= (int *) ((byte *)surface + surface->ofsTriangles);
 	indexes		= surface->numTriangles * 3;