made it compile if arduino decides to include files in a differnt order. DEC HEX and stuff now defined in MarlinSerial.h

Marlin/MarlinSerial.h

 
 #include <inttypes.h>
 #include <Stream.h>
+#include <string.h>
 #define  FORCE_INLINE __attribute__((always_inline)) inline
 
+#include "WString.h"
+
+#define DEC 10
+#define HEX 16
+#define OCT 8
+#define BIN 2
+#define BYTE 0
+
 
 
 // Define constants and variables for buffering incoming serial data.  We're