SilcBuffer silc_argument_payload_encode_one(SilcBuffer args,
                                                unsigned char *arg,
                                                SilcUInt32 arg_len,
                                                SilcUInt32 arg_type);

    Same as silc_argument_payload_encode but encodes one argument to
    the buffer `args' and returns the buffer.  The returned buffer
    may be different than the `args'.  If `args' is NULL for the first
    argument this allocates the buffer and returns it.