small renaming in the option doc

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13239 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Implement memoization for expand_module to improve performance

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13240 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02