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/qt/notificator.h

@@ -9,11 +9,12 @@
 #include "bitcoin-config.h"
 #endif
 
-#include <QObject>
 #include <QIcon>
+#include <QObject>
 
 QT_BEGIN_NAMESPACE
 class QSystemTrayIcon;
+
 #ifdef USE_DBUS
 class QDBusInterface;
 #endif