Enable hide according to http://doc.qt.io/qt-5/highdpi.html (#4110)

* Enable hide according to http://doc.qt.io/qt-5/highdpi.html

* Also enable Retina support for OS X

companion/src/simulator.cpp

@@ -70,6 +70,9 @@ void showMessage(const QString & message, enum QMessageBox::Icon icon = QMessage
 int main(int argc, char *argv[])
 {
   Q_INIT_RESOURCE(companion);
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0))
+  QApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+#endif
 
   QApplication app(argc, argv);
   app.setApplicationName("OpenTX Simulator");