Add option to disable volume control

src/core/player.h

@@ -102,6 +102,7 @@ class PlayerInterface : public QObject {
   void Stopped();
   void Error();
   void PlaylistFinished();
+  void VolumeEnabled(bool);
   void VolumeChanged(int volume);
   void Error(const QString &message);
   void TrackSkipped(PlaylistItemPtr old_track);
@@ -206,10 +207,11 @@ class Player : public PlayerInterface {
 
  private:
   Application *app_;
-  QSettings settings_;
   AnalyzerContainer *analyzer_;
   Equalizer *equalizer_;
 
+  QSettings settings_;
+
   PlaylistItemPtr current_item_;
 
   std::unique_ptr<EngineBase> engine_;
@@ -228,6 +230,8 @@ class Player : public PlayerInterface {
   PreviousBehaviour menu_previousmode_;
   int seek_step_sec_;
 
+  bool volume_control_;
+
 };
 
 #endif  // PLAYER_H