question about arduino due and function itoa

Hardware Arduino Due
1

Hi guys,
I was trying to compile board Arduino Due with the most updated compiler V1.5.2, but the error happends like error: 'itoa' was not declared in this scope. But if I selected Arduino 2560, everything is good. Anyone can help me with this, actually this is my dad's question, he just can't find any help from Chinese arduino forum. Thanks guys! Here are my codes:

#include <stdlib.h>
void setup() {
Serial.begin(9600);

char y1[3];
//String y1;
String y;
int L=9;
itoa(L,y1,16);
y=y1;
if (y.length()==1){y="0"+y;}
y.toUpperCase();
Serial.print("L hex=");
Serial.print(y);
}

void loop() {
}

2

That's a really long-winded way of writing Serial.println (L, HEX);

3

sorry, that's not what i need. For the code, I want get two digits result of L. For example, if L is E, it should be printed out 0E.

4

Two extra lines of code required.