Runtime: performance improvement in caml_blit_string
Runtime: performance improvement in caml_blit_string

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