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/walletview.cpp

@@ -21,7 +21,11 @@
 #include <QHBoxLayout>
 #include <QVBoxLayout>
 #include <QAction>
+#if QT_VERSION < 0x050000
 #include <QDesktopServices>
+#else
+#include <QStandardPaths>
+#endif
 #include <QFileDialog>
 #include <QPushButton>
 
@@ -232,7 +236,11 @@ void WalletView::encryptWallet(bool status)
 
 void WalletView::backupWallet()
 {
+#if QT_VERSION < 0x050000
     QString saveDir = QDesktopServices::storageLocation(QDesktopServices::DocumentsLocation);
+#else
+    QString saveDir = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
+#endif
     QString filename = QFileDialog::getSaveFileName(this, tr("Backup Wallet"), saveDir, tr("Wallet Data (*.dat)"));
     if (!filename.isEmpty()) {
         if (!walletModel->backupWallet(filename)) {