Another small change to MsgThread API.

Threads will now reliably get a call to DoFinish() no matter how the
thread terminates. This will always be called from within the thread,
whereas the destructor is called from the main thread after the child
thread has already terminated.

Also removing debugging code.

However, two problems remain with the ASCII writer (seeing them only
on MacOS):

    - the #start/#end timestamps contain only dummy values right now.
      The odd thing is that once I enable strftime() to print actual
      timestamps, I get crashes (even though strftime() is supposed to
      be thread-safe).

    - occassionally, there's still output missing in tests. In those
      cases, the file descriptor apparently goes bad: a write() will
      suddently return EBADF for reasons I don't understand yet.

src/threading/MsgThread.cc

@@ -155,8 +155,6 @@ void MsgThread::OnPrepareStop()
 	if ( finished || Killed() )
 		return;
 
-	// XX fprintf(stderr, "Sending FINISH to thread %s  ...\n", Name());
-
 	// Signal thread to terminate and wait until it has acknowledged.
 	SendIn(new FinishMessage(this, network_time), true);
 	}
@@ -356,7 +354,14 @@ void MsgThread::Run()
 		delete msg;
 		}
 
-	Finished();
+	// In case we haven't send the finish method yet, do it now. Reading
+	// global network_time here should be fine, it isn't changing
+	// anymore.
+	if ( ! finished )
+		{
+		OnFinish(network_time);
+		Finished();
+		}
 	}
 
 void MsgThread::GetStats(Stats* stats)