Fixed Mac OS-X build
Make sure trace level is reset to default (zero) on shutdown so when re-initialised it does not get spurious logs.
Changed test for QWAVE (QoS) support in Windows. In Windows Server 2008 R2 it is an optional component so may or may not be installed. Juts checking OS version not sufficient. Now we check for if we can load QWAVE.DLL before trying it.