Makefile: do not fail when trying to clean an unbuild documentation
Makefile: do not fail when trying to clean an unbuild documentation

Ignore-this: c2c8745f4e7b7d51102e882df16fcbfc

darcs-hash:20110701152636-da4f2-9632b45c053ef461a2c5cc44fb31273d17e9742a

OCamlPro-Henry/js_of_ocaml,alainfrisch/js_of_ocaml,alainfrisch/js_of_ocaml,alainfrisch/js_of_ocaml,alainfrisch/js_of_ocaml,OCamlPro-Henry/js_of_ocaml,OCamlPro-Henry/js_of_ocaml,OCamlPro-Henry/js_of_ocaml,OCamlPro-Henry/js_of_ocaml,alainfrisch/js_of_ocaml