Sound Blaster DSP write status emulation fixed up. DSP highspeed DMA
playback is also considered. Added bugfix for SB16 "require IRQ ack"
where audio is stopped if another IRQ is fired and the previous IRQ has
not been acked, which makes sense to me, and also eliminates popping and
crackling in the audio when using the auto-init DSP playback modes.
Added code to modify DSP busy wait delay if using DSP command 0x10
direct DAC output to rate-limit programs that use it and the IRQ 0 timer
for playback. The rate limit ensures that playback cannot happen faster
than 23000Hz just like real hardware when using DSP command 0x10.

Confirmed: Sound Blaster audio is now working with Crystal Dream demo,
though with very minor popping and crackling, which I will look into.