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/alert.cpp

@@ -2,17 +2,20 @@
 // Alert system
 //
 
+#include "alert.h"
+
+#include "key.h"
+#include "net.h"
+#include "ui_interface.h"
+#include "util.h"
+
 #include <algorithm>
+#include <inttypes.h>
+#include <map>
+
 #include <boost/algorithm/string/classification.hpp>
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/foreach.hpp>
-#include <map>
-
-#include "alert.h"
-#include "key.h"
-#include "net.h"
-#include "sync.h"
-#include "ui_interface.h"
 
 using namespace std;
 
@@ -48,8 +51,8 @@ std::string CUnsignedAlert::ToString() const
     return strprintf(
         "CAlert(\n"
         "    nVersion     = %d\n"
-        "    nRelayUntil  = %"PRI64d"\n"
-        "    nExpiration  = %"PRI64d"\n"
+        "    nRelayUntil  = %"PRId64"\n"
+        "    nExpiration  = %"PRId64"\n"
         "    nID          = %d\n"
         "    nCancel      = %d\n"
         "    setCancel    = %s\n"