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/addressbookpage.h

@@ -7,17 +7,19 @@
 
 #include <QDialog>
 
+class AddressTableModel;
+class OptionsModel;
+
 namespace Ui {
     class AddressBookPage;
 }
-class AddressTableModel;
 
 QT_BEGIN_NAMESPACE
-class QTableView;
 class QItemSelection;
-class QSortFilterProxyModel;
 class QMenu;
 class QModelIndex;
+class QSortFilterProxyModel;
+class QTableView;
 QT_END_NAMESPACE
 
 /** Widget that shows a list of sending or receiving addresses.