PR#6502: spurious warning on "use_menhir" tag

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15044 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#6474: fix the "weak dependencies" support (patch by Leo White)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15045 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#6509: Add -linkall flag to ocamlcommon archives (Patch by Frédéric Bour)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15047 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02