- Move replication code out of log.h and log.cc.
- Remove MYSQL_LOG and move implementation to MYSQL_QUERY_LOG
  and MYSQL_BINARY_LOG.
- Move Log_throttle, log_slow_applicable(), log_slow_statement()
  and log_slow_do() to log.h/log.cc.
- Cleanup interaction between sys_vars and log, move code from sys_vars to log.
- Make usage of LOCK_global_system_variables & LOCK_logger more consistent.
- Remove external access to LOCK_logger.
- Early exit if logs are closed (e.g. don't lock mutexes).
- Cleanup construction/destruction.
- Use common code for reopen/flush.
- Simplify LOGGER implementation - use enum_log_table_type more.
- Remove some global functions, use LOGGER functions directly.
- Make everything but LOGGER private.
- Write to error log without using log_event_handler since we only support
  error logging to file anyway.
- Splitt error logging and slow/general log (LOGGER).
- Simplify error logging functions.
- Remove sql_print_message_handlers[].
- Remove dead code.
- Update log.h/log.cc according to current code standard.
- Use true/false rather than TRUE/FALSE.
- Use bool rather than my_bool.
- Use size_t.
- Indentation/spacing cleanup.
- Move function documentation to header file and make into doxygen.
- Improve code documentation, add missing doxygen.
- Add documentation of query logging sysvars.
- Add simple unit test for Log_throttle
- Renames:
  opt_log => opt_general_log
  opt_logname => opt_general_logname
  opt_log_raw => opt_general_log_raw
  mysql_log => mysql_general_log
  key_file_query_log => key_file_general_log
  LOGGER => Query_logger
  MYSQL_QUERY_LOG => File_query_log
  event_coordinates => rpl_event_coordinates