Allow QSystemTrayIcon to be created on heap

... with a QApplication as parent.

This currently leads to a crash at the exit:

lass TestApp : public QApplication
{
Q_OBJECT

QIcon icon;
QSystemTrayIcon *tray_icon;
QTimer timer;

public:
TestApp(int &argc, char *argv[]) : QApplication(argc, argv)

{ icon.addFile("icon.png"); tray_icon = new QSystemTrayIcon(icon, this); tray_icon->show(); connect(&timer, SIGNAL(timeout()), this, SLOT(quit())); timer.start(2000); }

~TestApp() { }
};