typedef SilcBool (*SilcLogDebugCb)(char *file, char *function, int line,
                                       char *message, void *context);

    The debug logging callback function.  The default behaviour is to
    output messages to stderr.  `file', `function', and `line' are the
    corresponding offsets in the source files.  `message' points to a
    null-terminated buffer containing the debugging message, and `context'
    is the caller-specified context.

    The message must not be modified or freed by the callback function.
    If the function returns TRUE, SilcLog will assume the message as handled
    and won't run its default handler.

    silc_debug, silc_log_set_debug_callbacks