MXS-839: Store additional server information in mysqlmon

Mysqlmon now stores the values of read_only, slave_sql_running,
slave_io_running, the name and position of the masters binlog and the
replication configuration status of the slave.

This allows more detailed server information to be displayed with the
`show monitor <name>` diagnostic interface. In addition to this, the new
structure used to store them provides an easy way to store information
that is specific to a monitor and the servers it monitors.

These new status variables can be used to implement better multi-master
detection in mysqlmon by using the value of read_only to resolve
situations where multiple master candidates are available.

server/modules/monitor/mysqlmon.h

@@ -28,6 +28,7 @@
 #include <modinfo.h>
 #include <maxconfig.h>
 #include <externcmd.h>
+#include <hashtable.h>
 
 /**
  * @file mysqlmon.h - The MySQL monitor
@@ -69,6 +70,7 @@ typedef struct
     MONITOR_SERVERS *master; /**< Master server for MySQL Master/Slave replication */
     char* script; /*< Script to call when state changes occur on servers */
     bool events[MAX_MONITOR_EVENT]; /*< enabled events */
+    HASHTABLE *server_info; /**< Contains server specific information */
 } MYSQL_MONITOR;
 
 #endif