corrected Fwd/Rev LED logic in NmraDccMultiFunctionMotorDecoder example

added conditional compilation to use the newer Dcc.pin() method that used digitalPinToInterrupt() to determine the Ext Interrupt Number based on Arduino Pin to reduce confusion

examples/DCCInterface_TurntableControl/DCCInterface_TurntableControl.ino

@@ -19,6 +19,9 @@
 #include <AccelStepper.h>
 #include <NmraDcc.h>
 
+// Define the Arduino input Pin number for the DCC Signal 
+#define DCC_PIN     2
+
 // The lines below define the pins used to connect to the A4988 driver module
 #define A4988_STEP_PIN      4
 #define A4988_DIRECTION_PIN 5
@@ -243,8 +246,14 @@ void setupDCCDecoder()
 {
   Serial.println(F("Setting up DCC Decorder..."));
 
-  // Setup which External Interrupt, the Pin it's associated with that we're using and enable the Pull-Up 
-  Dcc.pin(0, 2, 1);
+  // Setup which External Interrupt, the Pin it's associated with that we're using and enable the Pull-Up
+  // Many Arduino Cores now support the digitalPinToInterrupt() function that makes it easier to figure out the
+  // Interrupt Number for the Arduino Pin number, which reduces confusion. 
+#ifdef digitalPinToInterrupt
+  Dcc.pin(DCC_PIN, 0);
+#else
+  Dcc.pin(0, DCC_PIN, 1);
+#endif
   
   // Call the main DCC Init function to enable the DCC Receiver
   Dcc.init( MAN_ID_DIY, 10, CV29_ACCESSORY_DECODER | CV29_OUTPUT_ADDRESS_MODE, 0 );