Fix to bug #549, http://bugs.skysql.com/show_bug.cgi?id=549

Each monitor loops 10 times/second (sleep 100ms) and perform monitoring checks only when monitor's interval is spent. Monitors notice faster if the shutdown flag is set and thus overall shutdown is faster.
hint.c:added missing header
Changed interval from unsigned long to size_t which is guaranteed to be of same size also in windows (if possible).
Added states to monitor object to make debugging and adding checks easier. Changed state macro to named enumerated type.