Add utilities for extension and attributes.
Add utilities for extension and attributes.

yunxing/ocaml,gerdstolpmann/ocaml,msprotz/ocaml,eliberis/ocaml,eliberis/ocaml,eliberis/ocaml,msprotz/ocaml,gerdstolpmann/ocaml,yunxing/ocaml,msprotz/ocaml,yunxing/ocaml,gerdstolpmann/ocaml,yunxing/ocaml,yunxing/ocaml,eliberis/ocaml,gerdstolpmann/ocaml,eliberis/ocaml,msprotz/ocaml,gerdstolpmann/ocaml,msprotz/ocaml