void silc_client_command_pending(SilcClientConnection conn,
                                     SilcCommand reply_cmd,
                                     SilcUInt16 ident,
                                     SilcCommandCb callback,
                                     void *context);

    This function can be used to add pending command callback to be
    called when an command reply is received to an earlier sent command.
    The `reply_cmd' is the command that must be received in order for
    the pending command callback indicated by `callback' to be called.
    The `callback' will deliver the `context' and
    SilcClientCommandReplyContext which includes the internals of the
    command reply.

    The `ident' is a command identifier which was set for the earlier
    sent command.  The command reply will include the same identifier
    and pending command callback will be called when the reply is
    received with the same command identifier.  It is possible to
    add multiple pending command callbacks for same command and for
    same identifier.

    Application may use this function to add its own command reply
    handlers if it wishes not to use the standard `command_reply'
    client operation.  However, note that the pending command callback
    does not deliver parsed command reply, but application must parse
    it itself.

    Note also that the application is notified about the received command
    reply through the `command_reply' client operation before calling
    the `callback` pending command callback.  That is the normal
    command reply handling, and is called regardless whether pending
    command callbacks are used or not.

    Commands that application calls with silc_client_command_call
    will use a command identifier from conn->cmd_ident variable.  After
    calling the silc_client_command_call, the conn->cmd_ident includes
    the command identifier that was used for the command sending.

    silc_client_command_call(client, conn, "PING silc.silcnet.org");
    silc_client_command_pending(conn, SILC_COMMAND_PING, conn->cmd_ident,
                                my_ping_handler, my_ping_context);