Make marking songs unavailable optional

src/settings/collectionsettingspage.h

@@ -2,6 +2,7 @@
  * Strawberry Music Player
  * This file was part of Clementine.
  * Copyright 2010, David Sansome <me@davidsansome.com>
+ * Copyright 2018-2019, Jonas Kvinge <jonas@jkvinge.net>
  *
  * Strawberry is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -18,19 +19,16 @@
  *
  */
 
-#ifndef LIBRARYSETTINGSPAGE_H
-#define LIBRARYSETTINGSPAGE_H
+#ifndef COLLECTIONSETTINGSPAGE_H
+#define COLLECTIONSETTINGSPAGE_H
 
 #include "config.h"
 
 #include <stdbool.h>
 #include <QObject>
-#include <QString>
 
 #include "settingspage.h"
 
-class QModelIndex;
-
 class SettingsDialog;
 class Ui_CollectionSettingsPage;
 
@@ -63,4 +61,4 @@ private:
   bool initialised_model_;
 };
 
-#endif // LIBRARYSETTINGSPAGE_H
+#endif  // COLLECTIONSETTINGSPAGE_H