Fix #5421: do not leak fds in various open_proc* functions.
Fix #5421: do not leak fds in various open_proc* functions.

Patch by Till Varoquaux <till@janestreet.com>

git-svn-id: e7e61699ce1738538ffebb75374fbea0924bc775@12038 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02

yallop/camlp4,yunxing/ocaml,gerdstolpmann/ocaml,eliberis/ocaml,yunxing/ocaml,yunxing/ocaml,eliberis/ocaml,yunxing/ocaml,msprotz/ocaml,msprotz/ocaml,msprotz/ocaml,hhugo/camlp4,eliberis/ocaml,eliberis/ocaml,gerdstolpmann/ocaml,msprotz/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,eliberis/ocaml,msprotz/ocaml,yunxing/ocaml,gerdstolpmann/ocaml,chambart/camlp4