[zBoy r137] initial sound support (Adventure Island II)

This is a preview of zBoy's sound support, as I implemented in version r137. It is the first time that zBoy emits any sound at all. It is still buggy, doesn't sound very pleasant and handles only 2 channels (out of 4). But it works! Further development will undoubtedly lead to plenty of improvements.
zboy.sourceforg...

[@dmitryhetman1509]

Nice graphics!