add code to record to struct min/max sample rates in various SB modes to
reflect recent testing, and to know whether or not high-speed DSP
commands matter.
update sample rate list for gui. fix some "capability" bugs in the
library.
consolidate "will DSP nag logic" into a function. replace test program
call to send buffer again with one IRQ handler call the library uses to
then re-send the buffer, so that if we're nagging the DSP from the main
idle function, we can NOT do anything from the IRQ to avoid crashes and
hangs. Add code to clarify why DSP nag mode is not recommended for DSP
4.xx playback on SB16 cards.