Fixing a rotation race condition at termination.

Noticed with DS, but could just as well happen with ASCII.

src/threading/Manager.h

@@ -77,6 +77,12 @@ public:
 	 */
 	int NumThreads() const { return all_threads.size(); }
 
+	/** Manually triggers processing of any thread input. This can be useful
+	 *  if the main thread is waiting for a specific message from a child.
+	 *  Usually, though, one should avoid using it.
+	 */
+	void ForceProcessing() { Process(); }
+
 protected:
 	friend class BasicThread;
 	friend class MsgThread;