do not emit parameter name for functions taking no arguments
do not emit parameter name for functions taking no arguments

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