The THREAD type was not used everywhere and pthread_t was used instead.
The thread creation function also returned the address of a stack allocated
value which isn't guaranteed to be usable.
When MaxScale perceives a state change in one of the servers it will log
an message into the log file stating the previous and the current state.
This will make it easier to analyze failures in the cluster.
The change to the mysql.user table in MySQL 5.7 caused MaxScale to stop
working with it. This commit adds functionality that checks which version of
the user data query should be made. It also moves common code related to
server version strings to server.c
The log manager variables lm_enabled_log_files_bitmask, log_ses_count
and tls_log_info that earlier were declared separately in every
c-file are now declared in the log_manager.h header.
