Adapt to OPL3DUO (serial control OPL3 actual hardware)

[denjhang]

https://github.com/DhrBaksteen/ArduinoOPL2/blob/master/examples/OPL3Duo/SerialPassthrough/SerialPassthrough.ino
https://github.com/DhrBaksteen/ArduinoOPL2/blob/master/examples/OPL2AudioBoard/SerialPassthrough/SerialPassthrough.ino

Currently I use SerialPassthrough.ino of OPL3DUO, compile these codes with arduino and upload them to arduino nano.
After that I use dosbox-x and specify the port number (like com3) and I can use the actual opl3 hardware.

[denjhang]

By the way, OPL3BankEditor actually already supports this feature.

[Wohlstand]

I will need to make use of extra chip interfaces, and make a different workflow way:

• for the case of emulated playback, I rely on sound output processing
• for the case of playing on real hardware, I will need to implement real-time processing (without using a built-in file player), OR, I'll just keep the real-time interface being used as a direct map to actual hardware, and you will need an external MIDI player program to use it.

[Wohlstand]

Seems a duplicate of #246.