ocamlbuild: explicit 'linkpkg' and 'dontlink(foo)' flags

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.02@15711 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#6717: Pprintast does not print let-pattern attributes

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.02@15712 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#6720: pass -g to C compilers when tag 'debug' is set

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.02@15713 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Update Changes after trunk cherry-picking session

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.02@15714 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02