Fix PR#6466: Non-exhaustive matching warning message for open types is confusing

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.02@15226 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Fix PR#6547: __MODULE__ aborts the compiler if the module name cannot be inferred

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.02@15227 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02