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/bitcoin.cpp

@@ -17,7 +17,9 @@
 #include "splashscreen.h"
 
 #include <QMessageBox>
+#if QT_VERSION < 0x050000
 #include <QTextCodec>
+#endif
 #include <QLocale>
 #include <QTimer>
 #include <QTranslator>
@@ -118,9 +120,11 @@ int main(int argc, char *argv[])
     // Command-line options take precedence:
     ParseParameters(argc, argv);
 
+#if QT_VERSION < 0x050000
     // Internal string conversion is all UTF-8
     QTextCodec::setCodecForTr(QTextCodec::codecForName("UTF-8"));
     QTextCodec::setCodecForCStrings(QTextCodec::codecForTr());
+#endif
 
     Q_INIT_RESOURCE(bitcoin);
     QApplication app(argc, argv);