Added pinToInterrupt() variant macro (Paul Stoffregen)

Author: cmaglie

hardware/arduino/avr/variants/mega/pins_arduino.h

@@ -83,6 +83,8 @@ static const uint8_t A15 = 69;
                                 ( (((p) >= 62) && ((p) <= 69)) ? ((p) - 62) : \
                                 0 ) ) ) ) ) )
 
+#define digitalPinToInterrupt(p) ((p) == 2 ? 0 : ((p) == 3 ? 1 : ((p) >= 18 && (p) <= 21 ? 23 - (p) : -1)))
+
 #ifdef ARDUINO_MAIN
 
 const uint16_t PROGMEM port_to_mode_PGM[] = {
@@ -360,4 +362,4 @@ const uint8_t PROGMEM digital_pin_to_timer_PGM[] = {
 
 #endif
 
-#endif
+#endif