feat: add itoa.h

Fixes #3084.

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

cores/arduino/wiring.h

@@ -28,6 +28,7 @@
 
 #include "api/Common.h"
 #include "api/deprecated-avr-comp/avr/dtostrf.h"
+#include "api/itoa.h"
 #include "clock.h"
 #include "dwt.h"
 #include "interrupt.h"