Bug #1313, fix typo (wrong variable name) in example.

Doc/lib/liblogging.tex

@@ -430,7 +430,7 @@ logged messages. For example:
 \begin{verbatim}
  FORMAT = "%(asctime)-15s %(clientip)s %(user)-8s %(message)s"
  logging.basicConfig(format=FORMAT)
- dict = { 'clientip' : '192.168.0.1', 'user' : 'fbloggs' }
+ d = { 'clientip' : '192.168.0.1', 'user' : 'fbloggs' }
  logger = logging.getLogger("tcpserver")
  logger.warning("Protocol problem: %s", "connection reset", extra=d)
 \end{verbatim}