Q2 cd audio bug fix

[Barnes]

Some q2 engines (q2e, bers@q2) under win8.1 or high have bug in cd audio code - no realtime value change, code return error
To fix
in CDAudio_GetMixerVolume
found
mxControlDetails.cbDetails = sizeof(mxValue);
and cange to
mxControlDetails.cbDetails = sizeof(MIXERCONTROLDETAILS_UNSIGNED);