Move buffer management code into DZAudioQueueBufferList
 seperate these code from the audio queue player.
 [TODO] add seek function to the audio queue player.
 [TODO] refine data feeding logic in DZAudioPlayer.
	1. whether buffer is overloaded shall be judged by DZAudioPlayer.
	2. whether audio queue should be paused waiting data, too by DZAudioPlayer.