PR#6495: add a safe_string tag to ocamlbuild (patch by Anil Madhavapeddy)

It kicks in for interface inference and compiler invocations.
safe_string does also alter the output of inferred types if
short_paths is used (since "bytes" is shorter than "string"),
but this requires a change to the ocamldoc driver and isn't
addressed in this PR.

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15053 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#6495: also add unsafe_string tag to ocamlbuild

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15054 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
ocamlbuild: add no_alias_deps tag (patch by Daniel Bünzli)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15055 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
update Changes

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15056 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02