fixed bug in native caml_raise_with_string, and synced code in byterun/fail.c for that function

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14772 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
add Changes note for the patch in rev 14772

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14773 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02