Merge pull request #137 from ocsigen/ocamlbuild-4.02

Fix the compilation of the ocamlbuild plugin with ocaml 4.02
Runtime: fix wrt latest js_of_ocaml
Merge pull request #138 from ocsigen/runtime

Runtime: fix wrt latest js_of_ocaml
Avoid an ocamlbuild warning when using no_extra_syntaxes