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/walletview.h

@@ -9,17 +9,14 @@
 
 class BitcoinGUI;
 class ClientModel;
-class WalletModel;
-class TransactionView;
 class OverviewPage;
-class SendCoinsDialog;
 class ReceiveCoinsDialog;
+class SendCoinsDialog;
 class SendCoinsRecipient;
-class SignVerifyMessageDialog;
-class RPCConsole;
+class TransactionView;
+class WalletModel;
 
 QT_BEGIN_NAMESPACE
-class QLabel;
 class QModelIndex;
 QT_END_NAMESPACE