Update song_editor.h

A better way to update the play button icons, which requires less "if" checks and method calls in total.

include/song_editor.h

@@ -59,12 +59,12 @@ public:
 	songEditor( song * _song, songEditor * & _engine_ptr );
 	virtual ~songEditor();
 
+	void setPauseIcon( bool pause );
+
 
 public slots:
 	void scrolled( int _new_pos );
 
-	void updatePlayPauseIcon();
-
 
 private slots:
 	void setHighQuality( bool );