added "goldplay stereo" option as workaround for demos that use Sound
Blaster Pro but don't seem to know the requirement that they double the
sample rate when computing the DSP time constant. Such demos tend to
sound worse in stereo mode because they end up programming the DSP to
run at 11025Hz stereo while updating the audio sample byte at 22050Hz.
Enabling the option double the rate that the DMA memory location is read
to enable full quality playback with such demos.