Added loop audio buffer source field

Author: pavle-goloskokovic

v3/src/sound/webaudio/WebAudioSound.js

@@ -25,6 +25,13 @@ var WebAudioSound = new Class({
          * @property {AudioBufferSourceNode} source
          */
         this.source = null;
+        /**
+         * [description]
+         *
+         * @private
+         * @property {AudioBufferSourceNode} loopSource
+         */
+        this.loopSource = null;
         /**
          * [description]
          *