Use correct include headers

Some headers are overkilled, and the order should be

/* LibC */
include <stdxxx.h>

/* Framework */
include <os.h>

/* Local */
include "EthUstream.h"

src_common/uint256.c

@@ -19,6 +19,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+
 #include "uint256.h"
 
 static const char HEXDIGITS[] = "0123456789abcdef";