[openal] Synchronizing 3D sources

[Chris Robinson]

On 01/24/2014 04:34 AM, Doug Binks wrote:
> Makes sense. Since this needs new code for atomically getting a device
> timer etc., also adding code for this shouldn't be too much of an extra
> problem although it does add to device maintenance costs.

It should be fine to just add another field to ALCdevice, something like
ALuint64 SamplesMixed;
which would be initialized to 0 and incremented in aluMixData. Then when 
the clock time is queried, convert it using the device frequency.