minor clean-ups

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14642 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#5941: add Printexc.set_uncaught_exception_handler


git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14643 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02