Missing `passwd` fields for *BSD and macOS

[zacknewman]

OpenBSD and NetBSD define passwd as the following:

struct passwd {
    char *pw_name;
    char *pw_passwd;
    uid_t pw_uid;
    gid_t pw_gid;
    time_t pw_change;
    char *pw_class;
    char *pw_gecos;
    char *pw_dir;
    char *pw_shell;
    time_t pw_expire;
};

macOS, FreeBSD, and DragonFly BSD define passwd as the following:

struct passwd {
    char *pw_name;
    char *pw_passwd;
    uid_t pw_uid;
    gid_t pw_gid;
    time_t pw_change;
    char *pw_class;
    char *pw_gecos;
    char *pw_dir;
    char *pw_shell;
    time_t pw_expire;
    int pw_fields;
};

Currently passwd only conforms to how glibc and musl define it:

struct passwd {
    char *pw_name;
    char *pw_passwd;
    uid_t pw_uid;
    gid_t pw_gid;
    char *pw_gecos;
    char *pw_dir;
    char *pw_shell;
};

Should passwd be defined like below:

pub struct passwd {
    pub pw_name: *mut c_char,
    pub pw_passwd: *mut c_char,
    pub pw_uid: crate::uid_t,
    pub pw_gid: crate::gid_t,
    #[cfg(any(target_os = "dragonfly", target_os = "freebsd", target_os = "macos", target_os = "netbsd", target_os = "openbsd"))]
    pub pw_change: crate::time_t,
    #[cfg(any(target_os = "dragonfly", target_os = "freebsd", target_os = "macos", target_os = "netbsd", target_os = "openbsd"))]
    pub pw_class: *mut c_char,
    pub pw_gecos: *mut c_char,
    pub pw_dir: *mut c_char,
    pub pw_shell: *mut c_char,
    #[cfg(any(target_os = "dragonfly", target_os = "freebsd", target_os = "macos", target_os = "netbsd", target_os = "openbsd"))]
    pub pw_expire: crate::time_t,
    #[cfg(any(target_os = "dragonfly", target_os = "freebsd", target_os = "macos"))]
    pub pw_fields: c_int,
}