Add -verbose:monitor and silence the monitor logging by default.

Change-Id: If05c4853c6c072759fb6b7f301a583d6b8c55b9f
diff --git a/src/monitor.h b/src/monitor.h
index fefc43e..9ea407e 100644
--- a/src/monitor.h
+++ b/src/monitor.h
@@ -60,6 +60,8 @@
  public:
   ~Monitor();
 
+  static void SetVerbose(bool is_verbose);
+
   static uint32_t GetLockOwner(uint32_t raw_lock_word);
 
   static void MonitorEnter(Thread* thread, Object* obj);
@@ -91,6 +93,8 @@
 
   void Wait(Thread* self, int64_t msec, int32_t nsec, bool interruptShouldThrow);
 
+  static bool is_verbose_;
+
   /* Which thread currently owns the lock? */
   Thread* owner_;