void silc_log_set_debug_callbacks(SilcLogDebugCb debug_cb,
                                      void *debug_context,
                                      SilcLogHexdumpCb hexdump_cb,
                                      void *hexdump_context);

    Sets `debug_cb' as the the default callback function for the debug
    output, that will be called with the `debug_context' parameter.
    When SilcLog receives a debug message, it will trigger the callback
    function.  If the callback function returns TRUE SilcLog will assume
    the input as handled and won't run its default handler.  The `hexdump_cb'
    and `hexdump_context' works the same way, except that they are referred
    to SILC_LOG_HEXDUMP requests.

    You can disable/remove a callback by setting it to NULL.  If set, each
    callback function must be either in the form described by SilcLogDebugCb
    or SilcLogHexdumpCb.