Merge pull request phaserjs#3543 from rexrainbow/master

Add 'destroy' event of sound object

Author: photonstorm

CHANGELOG.md

@@ -45,6 +45,7 @@
 * Utils.Array.SetAll will set a property on all elements of an array to the given value, with optional range limits.
 * Utils.Array.Swap will swap the position of two elements in an array.
 * TransformMatrix.destroy is a new method that will clear out the array and object used by a Matrix internally.
+* Add 'destroy' event in sound object.
 
 ### Bug Fixes
 

src/sound/BaseSound.js

@@ -522,6 +522,7 @@ var BaseSound = new Class({
             return;
         }
 
+        this.emit('destroy', this);
         this.pendingRemove = true;
         this.manager = null;
         this.key = '';