add a clarification comment in bytecomp/simplif.ml
add a clarification comment in bytecomp/simplif.ml

See
  https://github.com/ocaml/ocaml/pull/517#issuecomment-235013881

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