Support Arduino OPL2 (OPL3) communication protocol.

[Denjhang Liu]

If it can support this, then I can easily use OPL3BankEditor to debug the YMF825 sound.

[Denjhang Liu]

https://github.com/DhrBaksteen/ArduinoOPL2

[Dan Fry]

Current development builds of OPL3BankEditor support the RetroWave OPL3 protocol, so it can already be used with opl2sd1.