FileAnalysis: insert explicit event queue flush points.

And added an event called "event_queue_flush_point" to mark where that
occured in the event stream.  The FAF now uses an explicit event queue
flush instead of buffering input in order to wait for a file handle to
be returned from script-layer.

src/file_analysis/Hash.cc

@@ -48,5 +48,5 @@ void Hash::Finalize()
 	vl->append(new StringVal(kind));
 	vl->append(hash->Get());
 
-	mgr.Dispatch(new Event(file_hash, vl));
+	mgr.QueueEvent(file_hash, vl);
 	}