Function s7_make_function 

pub unsafe extern "C" fn s7_make_function(
    sc: *mut s7_scheme,
    name: *const c_char,
    fnc: s7_function,
    required_args: s7_int,
    optional_args: s7_int,
    rest_arg: bool,
    doc: *const c_char,
) -> s7_pointer