Fixed sound issues, when Alt+Tabbed

When Alt+Tabbed the streaming sound will start to lag. This is because the main-loop speed is reduced, so there are not enough OpenAL soundbuffers available to fill on update().

I just set the number of buffers to 8. Maybe a better solution is, to move the openal code to a thread running at fixed speed? Or allocate buffers dynamically?

However, this will fix the stuttering sound for now.