Add explicit dependencies on the unix module to the examples.
Add explicit dependencies on the unix module to the examples.

sjfloat/ocaml-ctypes,yallop/ocaml-ctypes,ocamllabs/ocaml-ctypes,dsheets/ocaml-ctypes,dsheets/ocaml-ctypes,whitequark/ocaml-ctypes,fdopen/ocaml-ctypes,fdopen/ocaml-ctypes,sjfloat/ocaml-ctypes,ocamllabs/ocaml-ctypes,fdopen/ocaml-ctypes,dsheets/ocaml-ctypes,sjfloat/ocaml-ctypes,yallop/ocaml-ctypes,whitequark/ocaml-ctypes,whitequark/ocaml-ctypes