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).

server/core/gateway.c

@@ -1688,8 +1688,13 @@ static void log_flush_cb(
 static void unlink_pidfile(void)
 {
 	if (strlen(pidfile)) {
-		if (unlink(pidfile)) {
-			fprintf(stderr, "MaxScale failed to remove pidfile %s: error %d, %s\n", pidfile, errno, strerror(errno));
+		if (unlink(pidfile)) 
+		{
+			fprintf(stderr, 
+				"MaxScale failed to remove pidfile %s: error %d, %s\n", 
+				pidfile, 
+				errno, 
+				strerror(errno));
 		}
 	}
 }