message: add missing const in traceVolumeRay signature
diff: @@ -66,7 +66,7 @@ inline bool isOccluded(const World *uniform world, varying Ray &ray)
  return isOccluded(world, ray, NULL);
  }
  -inline void traceVolumeRay(World *uniform world,
  +inline void traceVolumeRay(const World *uniform world,
  varying Ray &ray,
  VolumeInterval &interval)
  {
  