Fix for when not producing local output; that hung.

* origin/topic/robin/dataseries:
  Moving trace for rotation test into traces directory.
  Fixing a rotation race condition at termination.
  Portability fixes.
  Extending DS docs with some examples.
  Updating doc.
  Fixing pack_scale and time-as-int.
  Adding format specifier to DS spec to print out double as %.6f.
  DataSeries updates and fixes.
  DataSeries tuning.
  Tweaking DataSeries support.
  Extending log post-processor call to include the name of the writer.
  Removing an unnecessary const cast.
  DataSeries TODO list with open issues/questions.
  Starting DataSeries HowTo.
  Additional test output canonification for ds2txt's timestamps.
  In threads, an internal error now immediately aborts.
  DataSeries cleanup.
  Working on DataSeries support.
  Merging in DataSeries support from topic/gilbert/logging.
  Fixing  threads' DoFinish() method.

src/threading/MsgThread.h

@@ -171,6 +171,8 @@ public:
 protected:
 	friend class Manager;
 	friend class HeartbeatMessage;
+	friend class FinishMessage;
+	friend class FinishedMessage;
 
 	/**
 	 * Pops a message sent by the child from the child-to-main queue.
@@ -215,6 +217,12 @@ protected:
 	 */
 	virtual bool DoHeartbeat(double network_time, double current_time);
 
+	/** Triggered for execution in the child thread just before shutting threads down.
+	 *  The child thread should finish its operations and then *must*
+	 *  call this class' implementation.
+	 */
+	virtual bool DoFinish();
+
 private:
 	/**
 	 * Pops a message sent by the main thread from the main-to-chold
@@ -270,6 +278,8 @@ private:
 
 	uint64_t cnt_sent_in;	// Counts message sent to child.
 	uint64_t cnt_sent_out;	// Counts message sent by child.
+
+	bool finished;	// Set to true by Finished message.
 };
 
 /**