Add mutexes

src/engine/enginebase.h

@@ -168,8 +168,6 @@ class EngineBase : public QObject {
 
   void TrackEnded();
 
-  void FadeoutFinishedSignal();
-
   void StatusText(const QString &text);
   void Error(const QString &text);
 
@@ -188,6 +186,8 @@ class EngineBase : public QObject {
 
   void VolumeChanged(const uint volume);
 
+  void Finished();
+
  protected:
   bool exclusive_mode_;
   bool volume_control_;