Very useful to determine if a mod should be doing something if your ("unit" => "player") dead or a ghost.
Returns 1 if "unit" is dead or a ghost, nil otherwise.
Does not work for ("pet") unless the pet bar is still active. Not sure why the petbar stays active when the pet dies -- it used to gray out, now it will disappear after some time or some event happens, but not immediately when the pet dies. -- 5/29/2006