Qt5 compatibility

This commit squashes all the changes in the Qt5 branch
relative to master.

Backward compatibility with Qt4 is retained.

Original authors:

- Philip Kaufmann <phil.kaufmann@t-online.de>
- Jonas Schnelli <jonas.schnelli@include7.ch>

src/qt/walletstack.h

@@ -40,6 +40,7 @@ QT_END_NAMESPACE
 class WalletStack : public QStackedWidget
 {
     Q_OBJECT
+
 public:
     explicit WalletStack(QWidget *parent = 0);
     ~WalletStack();