Add missing Noreturn qualifiers

(patch by Peter Zotov, review by Max Mouratov)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15057 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
implement {Bytes,String}.mapi

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15058 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02