bool silc_client_command_unregister(SilcClient client,
SilcCommand command,
SilcCommandCb command_function,
SilcCommandCb command_reply_function,
bool silc_client_command_unregister(SilcClient client,
SilcCommand command,
SilcCommandCb command_function,
SilcCommandCb command_reply_function,