Feature request: OPL4 hardware playback (via SPFM)

[denjhang]

I hope to add a function: use hardware OPL3 (SPFM+RE1-YMF262) + simulated PCM to play OPL4 music.

[denjhang]

I need such a function, just like YM2612 and YM2610, which can simulate PCM independently.

[kuma4649]

これは要望で。