- don't call glNormal unnecessarily

- do The Right Thing (TM) with the light position, i.e., set it
  *before* we multiply by the modelview matrix. It's much easier
  to achieve predictable lighting results like this: (-1,0,0)
  simply means "light from the left", (0,1,0) means "light from
  the top", (0,0,1) means "light from the front", etc.