Replay: grab reference to timestamp rather than timestamp

PARM messages would not have been updating the clock correctly
Also, random stack corruption...

Tools/Replay/MsgHandler.h

@@ -451,7 +451,7 @@ private:
 class MsgHandler_PARM : public MsgHandler
 {
 public:
-    MsgHandler_PARM(log_Format &_f, DataFlash_Class &_dataflash, uint64_t _last_timestamp_usec) : MsgHandler(_f, _dataflash, _last_timestamp_usec) {};
+    MsgHandler_PARM(log_Format &_f, DataFlash_Class &_dataflash, uint64_t &_last_timestamp_usec) : MsgHandler(_f, _dataflash, _last_timestamp_usec) {};
 
     virtual void process_message(uint8_t *msg);
 };