made atomic lock optional

fixed an incorrect merge to nativeApp.cpp

made atomic locks init correctly

reintroduced atomic locks in audio as an optional setting

converted global pointers to global objects on stack

moved all mixing code into PSPMixer

internaized all code into __sceAudio.cpp

cleaned up rebase

cleaned up rebase
Merge pull request #4206 from bollu/AudioArtefactFix

optional atomic audio locks