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/crypter.h

@@ -1,13 +1,15 @@
 // 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 __CRYPTER_H__
 #define __CRYPTER_H__
 
-#include "allocators.h" /* for SecureString */
-#include "key.h"
+#include "allocators.h"
 #include "serialize.h"
 
+class uint256;
+
 const unsigned int WALLET_CRYPTO_KEY_SIZE = 32;
 const unsigned int WALLET_CRYPTO_SALT_SIZE = 8;