Cleanup code using forward declarations.

Use misc methods of avoiding unnecesary header includes.
Replace int typedefs with int##_t from stdint.h.
Replace PRI64[xdu] with PRI[xdu]64 from inttypes.h.
Normalize QT_VERSION ifs where possible.
Resolve some indirect dependencies as direct ones.
Remove extern declarations from .cpp files.

src/hash.h

@@ -2,16 +2,19 @@
 // Copyright (c) 2009-2013 The Bitcoin developers
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
 #ifndef BITCOIN_HASH_H
 #define BITCOIN_HASH_H
 
-#include "uint256.h"
 #include "serialize.h"
+#include "uint256.h"
+#include "version.h"
 
-#include <openssl/sha.h>
-#include <openssl/ripemd.h>
 #include <vector>
 
+#include <openssl/ripemd.h>
+#include <openssl/sha.h>
+
 template<typename T1>
 inline uint256 Hash(const T1 pbegin, const T1 pend)
 {