Final GSoC commit.
* Bugfix: Negative frames crashed
* Bugfix: JOS sample buffer size prediction error (wasted memory)
* Optimisation: for JOS upsampling (around 12 % difference measured here)
* Optimisation: Better filter for JOS resampling
* Bugfix: Error in relative 3D audio code.
* Removed Attenuation
* Bugfix: Multiple scenes in BGE lead to errors, BGE audio now all relative, to support multiple scenes.