pub unsafe extern "C" fn libssh2_userauth_password_ex(
    session: *mut LIBSSH2_SESSION,
    username: *const c_char,
    username_len: c_uint,
    password: *const c_char,
    password_len: c_uint,
    password_change_cb: Option<LIBSSH2_PASSWD_CHANGEREQ_FUNC>
) -> c_int