BIND 10 #976: Add syslog appender to logging code

[BIND 10 Development]

#976: Add syslog appender to logging code
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                   Reporter:         |                 Owner:  UnAssigned
  stephen                            |                Status:  assigned
                       Type:  task   |             Milestone:
                   Priority:  major  |  Sprint-20110614
                  Component:         |            Resolution:
  logging                            |             Sensitive:  0
                   Keywords:         |           Sub-Project:  DNS
            Defect Severity:  N/A    |  Estimated Difficulty:  0.0
Feature Depending on Ticket:         |           Total Hours:  0
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Changes (by stephen):

 * owner:  stephen => UnAssigned


Comment:

 It turned out that log4cplus had the code for a syslog appender in the
 package, but it was not described in the
 [http://log4cplus.sourceforge.net/docs/html/annotated.html online
 documentation].  So adding the appender was fairly simple.  The test
 program (logger_example) was extended to check the syslog appender worked
 and to check its interaction with other appenders (although there are no
 automated unittests to check that the logging writes to syslog - this is
 difficult to achieve across multiple platforms.)  Using this, the
 opportunity was taken to extend the tests to check that the logging system
 can write to multiple destinations.  These tests revealed a problem with
 logger names reported in output messages, which was corrected.

 The changes made fall into the following categories:

 * Add the syslog appender.
 * Extend the logger tests to include testing that the logging code can
 write to multiple destinations simultaneously.
 * Correct the naming problem by altering the root logger mapping.
 Previously the BIND 10 root logger mapped to the log4cplus root logger,
 and the BIND 10 root logger name was specially inserted into logging
 messages.  However this gave problems when a message was logged with the
 BIND 10 root logger itself -  the messages appeared with the logger name
 "root".  The code now has been changed so that the BIND 10 root logger is
 now child of the log4cplus root logger (which does not log any messages):
 this makes all names appear correctly.
 * Extend the documentation.
 * Removed the files relating to the old log4cxx implementation.

 Commit 8a83c13c2037e69e64474131916b6c53ececef34 now ready for review.

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Ticket URL: <http://bind10.isc.org/ticket/976#comment:4>
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