add documentation

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/safe-string@14676 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
cleanup and formatting

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/safe-string@14677 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
(does not work) set up bytes=string in the initial environment instead of changing the type comparison functions

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/safe-string@14678 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02