Modernize deprecated header usage

pi2-demo/src/Map.cpp

@@ -3,11 +3,11 @@
 #include "MapAppABIWrapper.hpp"
 #include <algorithm>
 #include <chrono>
+#include <cstddef>
 #include <limits>
 #include <memory>
 #include <ratio>
 #include <sstream>
-#include <stddef.h>
 #include <stdexcept>
 #include <string>
 #include <thread>