last 2.2.1 snapshot

This will probably be the last version based on adplug 2.2.1 before I migrate to 2.3.1.

Note: I had to change the original signature of the "load" API to allow for the asynchronous load of
add-on "instrument" (etc) files. Other than that the adplug codebase is largely in its original state.

consolidated player version

Cleaned up plugin version for use with latest unified player.