Fixed a bug in Sync where we were using an object through a

reference to a shared pointer.  A deref of the shared ptr could
trigger the dtor of the object while threads are waiting.  Fixed that
by properly copying the shared ptr.

src/Synchronizer.h

@@ -51,11 +51,13 @@ class Synchronizer : public boost::noncopyable
         struct PendingOps
         {
             PendingOps(int flags);
+            ~PendingOps();
             int opFlags;
+            int waiters;
             bool finished;
             boost::condition condvar;
             void wait(boost::recursive_mutex *);
-            void notify(boost::recursive_mutex *);
+            void notify();
         };
         
         struct Job : public ThreadPool::Job