player control states fixed (when pressing next/prev button), refresh them in event driven way

src/com/jpexs/decompiler/flash/gui/player/MediaDisplay.java

@@ -1,16 +1,16 @@
 /*
  *  Copyright (C) 2010-2015 JPEXS
- * 
+ *
  *  This program is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation, either version 3 of the License, or
  *  (at your option) any later version.
- * 
+ *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
- * 
+ *
  *  You should have received a copy of the GNU General Public License
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
@@ -56,4 +56,8 @@ public interface MediaDisplay {
     public double getZoomToFit();
 
     public Zoom getZoom();
+
+    public void addEventListener(MediaDisplayListener listener);
+
+    public void removeEventListener(MediaDisplayListener listener);
 }