Fix compiler warning: implicit declaration of function

Fix #44
cores/arduino/wiring_digital.c:37:8: warning: implicit declaration of function 'is_pin_configured' [-Wimplicit-function-declaration]
     if(is_pin_configured(p, g_anOutputPinConfigured)) {

Signed-off-by: Frederic.Pillon <[email protected]>

Author: fpistm

cores/arduino/wiring_analog.c

@@ -17,6 +17,7 @@
  */
 
 #include "Arduino.h"
+#include "PinConfigured.h"
 
 #ifdef __cplusplus
 extern "C" {

cores/arduino/wiring_digital.c

@@ -17,6 +17,7 @@
 */
 
 #include "Arduino.h"
+#include "PinConfigured.h"
 
 #ifdef __cplusplus
  extern "C" {