SilcBuffer silc_command_payload_encode_va(SilcCommand cmd,
                                              SilcUInt16 ident,
                                              SilcUInt32 argc, ...);

    Encodes Command payload with variable argument list. The arguments
    must be: SilcUInt32, unsigned char *, unsigned int, ... One
    {SilcUInt32, unsigned char * and unsigned int} forms one argument,
    thus `argc' in case when sending one {SilcUInt32, unsigned char *
    and SilcUInt32} equals one (1) and when sending two of those it
    equals two (2), and so on. This has to be preserved or bad things
    will happen. The variable arguments is: {type, data, data_len}.