Fix setting output/device for Xine and VLC backend

- Fixed setting output and device on Xine and VLC backend
- Fixed track slider for Xine, VLC and Phonon
- Improved backend settings to better support multiple backends
- Added group by samplerate and bitdepth in collection
- Fixed crash on exit when existing instance of the application is already runnung caused by NVIDIA driver
- Changed Q_OS_MAC to Q_OS_MACOS

src/settings/shortcutssettingspage.cpp

@@ -72,7 +72,7 @@ GlobalShortcutsSettingsPage::~GlobalShortcutsSettingsPage() { delete ui_; }
 
 bool GlobalShortcutsSettingsPage::IsEnabled() const {
 
-#ifdef Q_OS_MAC
+#ifdef Q_OS_MACOS
   qLog(Debug) << Utilities::GetMacVersion();
   if (Utilities::GetMacVersion() < 6) {  // Leopard and earlier.
     return false;