Add support for AdLib Gold banks
It's another variant of AdLib's BNK bank format which stores 4-op instruments.
The working implementation from off GenAdldata: https://github.com/Wohlstand/libADLMIDI/blob/master/utils/gen_adldata/file_formats/load_bnk2.h
- [x] Read/import
- [ ] Writing
BNK2 takes a prefix to filter which instruments are going in the melodic or percussion bank. How to handle this? can I pop up a dialog box?
That filter was a workaround to "Master of Magic"'s bank, for now, let's just make the non-GM bank for debug purposes, and then look for the internals better...
JPCima have made experimental read-only: https://github.com/Wohlstand/OPL3BankEditor/pull/98