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/init.h

@@ -2,14 +2,18 @@
 // 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_INIT_H
 #define BITCOIN_INIT_H
 
 #include <string>
-#include <boost/thread.hpp>
 
 class CWallet;
 
+namespace boost {
+    class thread_group;
+};
+
 extern std::string strWalletFile;
 extern CWallet* pwalletMain;