core: remove includes in .cpp, if header is already in .h

- example: if util.h includes stdint.h, remove it from util.cpp, as
  util.h is the first header included in util.cpp

src/script.cpp

@@ -14,8 +14,6 @@
 #include "uint256.h"
 #include "util.h"
 
-#include <stdint.h>
-
 #include <boost/foreach.hpp>
 #include <boost/tuple/tuple.hpp>
 #include <boost/tuple/tuple_comparison.hpp>