Try solving AAC issues (Faad branch)

This branch is supposed to try different ways to decode aac audio in order to find a solution for AAC audio issue.

A new aac opensource decoder - FAAD is added and test in the project and comparing with ffmpeg.
Macro FAAD is used to active FAAD functions.
Currently, the output pcm of new decoder is just all right. dumped pcm file is also perfactly playable in cool audio. 
However, when playing the decoded pcm buffer in ppsspp, it is completely silent. we have to resample again with ffmpeg from s16 to s16 itself :O to get sound, but the sound quality is the same as the one using ffmpeg only. 
So, there are 3 questions:
1. why the faad's output can play perfactly into file but silence in memory?
2. why resampling from s16 to s16 with ffmpeg will have sound?
3. why the sound is still shaking after resampling? (but perfactly in dumped file again).  

Regarding to the so wired behaviors in this test, I begin to doubt that the problem could be in ppsspp, and possibly in the part of playing pcm stream.