replaygain + pad blocks

gistfile1.txt

            public bool ReplayGainEnabled {
                get { return rgvolume != null; }
                set {
                    if (value && rgvolume == null) {
                        visible_sink.SetBlocked (true, InsertReplayGain);
                        Log.Debug ("Enabled ReplayGain volume scaling.");
                    } else if (!value && rgvolume != null) {
                        visible_sink.SetBlocked (false, RemoveReplayGain);
                        Log.Debug ("Disabled ReplayGain volume scaling.");
                    }
                }
            }