Add KSM playing support

[Wohlstand]

This is a music format of Ken Silverman which uses OPL2 chip, PC Speaker, or just MIDI.

Here is a small pack of them and the source code of KSM related things, sample music files and the specification in the "KSMFORM.TXT", found at here http://advsys.net/ken/download.htm:
ksmsongs.zip

The "insts.dat" looks like another bank format that can be added into OPL3-BE 🤔

[Wohlstand]

btw, for a quick run, I'll try to make the KSM2IMF converter to play these songs here in a place.