fix IRQ interval vs sound card prepare. split prepare between buffer and play. Update set IRQ function to reject change if prepared (since prepare in SNDSB means we already told the DSP the block size).
fix IRQ interval vs sound card prepare. split prepare between buffer and
play. Update set IRQ function to reject change if prepared (since
prepare in SNDSB means we already told the DSP the block size).

joncampbell123/doslib,joncampbell123/doslib,joncampbell123/doslib,joncampbell123/doslib,joncampbell123/doslib,joncampbell123/doslib