Fix a typo in close_functions.
    
    (Patch by Evgeny Roubinchtein)
    
    The typo isn't a bug since the variables `arity' and `body' are never
    actually referenced in the body of the function, but it does
    (negatively) affect readability of the code.
    
    git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14430 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02