Fix the behavior of Unix.read on Windows
Fix the behavior of Unix.read on Windows

This fixes Mantis PR #7342

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