Addition of notifyServceMode call to allow decoders to turn off high current outputs (#14)

* Add notification for entering and leaving service mode to allow the
decoder to swithc off high current outputs

* Add notification for entering and leaving service mode to allow the
decoder to swithc off high current outputs

NmraDcc.cpp

@@ -927,10 +927,18 @@ void processServiceModeOperation( DCC_MSG * pDccMsg )
 #endif
 void resetServiceModeTimer(uint8_t inServiceMode)
 {
+  if (notifyServiceMode && inServiceMode != DccProcState.inServiceMode)
+  {
+    notifyServiceMode(inServiceMode);
+  }
   // Set the Service Mode
   DccProcState.inServiceMode = inServiceMode ;
   
   DccProcState.LastServiceModeMillis = inServiceMode ? millis() : 0 ;
+  if (notifyServiceMode && inServiceMode != DccProcState.inServiceMode)
+  {
+    notifyServiceMode(inServiceMode);
+  }
 }
 
 void clearDccProcState(uint8_t inServiceMode)

NmraDcc.h

@@ -669,6 +669,7 @@ extern void    notifyCVResetFactoryDefault(void) __attribute__ ((weak));
  *    None
  */
 extern void    notifyCVAck(void) __attribute__ ((weak));
+extern void    notifyServiceMode(bool) __attribute__ ((weak));
 
 #if defined (__cplusplus)
 }