Improved signal handling.

Sending SIGTERM triggers a normal shutdown of all threads that waits
until they have processed their remaining data. However, sending a 2nd
SIGTERM while waiting for them to finish will immediately kill them
all.

src/threading/Manager.h

@@ -43,6 +43,21 @@ public:
 	 */
 	void Terminate();
 
+	/**
+	 * Returns True if we are currently in Terminate() waiting for 
+	 * threads to exit.
+	 */
+	bool Terminating() const	{ return terminating; }
+
+	/**
+	 * Immediately kills all child threads. It does however not yet join
+	 * them, one still needs to call Terminate() for that.
+	 *
+	 * This method is safe to call from a signal handler, and can in fact
+	 * be called while Terminate() is already in progress.
+	 */
+	void KillThreads();
+
 	typedef std::list<std::pair<string, MsgThread::Stats> > msg_stats_list;
 
 	/**
@@ -115,6 +130,7 @@ private:
 
 	bool did_process;	// True if the last Process() found some work to do.
 	double next_beat;	// Timestamp when the next heartbeat will be sent.
+	bool terminating;	// True if we are in Terminate().
 
 	msg_stats_list stats;
 };