Add 5ms callback registration for precise audio updates

include/boo/audiodev/IAudioVoiceEngine.hpp

@@ -35,6 +35,9 @@ struct IAudioVoiceEngine
     /** Client calls this to allocate a Submix for gathering audio together for effects processing */
     virtual std::unique_ptr<IAudioSubmix> allocateNewSubmix(IAudioSubmixCallback* cb=nullptr)=0;
 
+    /** Client may optionally register a 200-virtual-updates each second callback for the stream */
+    virtual void register5MsCallback(std::function<void(double dt)>&& callback)=0;
+
     /** Client may use this to determine current speaker-setup */
     virtual AudioChannelSet getAvailableSet()=0;