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/checkpoints.cpp

@@ -2,14 +2,16 @@
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <boost/assign/list_of.hpp> // for 'map_list_of()'
-#include <boost/foreach.hpp>
-
 #include "checkpoints.h"
 
 #include "main.h"
 #include "uint256.h"
 
+#include <stdint.h>
+
+#include <boost/assign/list_of.hpp> // for 'map_list_of()'
+#include <boost/foreach.hpp>
+
 namespace Checkpoints
 {
     typedef std::map<int, uint256> MapCheckpoints;
@@ -23,8 +25,8 @@ namespace Checkpoints
 
     struct CCheckpointData {
         const MapCheckpoints *mapCheckpoints;
-        int64 nTimeLastCheckpoint;
-        int64 nTransactionsLastCheckpoint;
+        int64_t nTimeLastCheckpoint;
+        int64_t nTransactionsLastCheckpoint;
         double fTransactionsPerDay;
     };
 
@@ -105,7 +107,7 @@ namespace Checkpoints
         if (pindex==NULL)
             return 0.0;
 
-        int64 nNow = time(NULL);
+        int64_t nNow = time(NULL);
 
         double fWorkBefore = 0.0; // Amount of work done before pindex
         double fWorkAfter = 0.0;  // Amount of work left after pindex (estimated)