Add Events e.g. `onSpeedZero` or `onLooping`

[PeterNerlich]

I suggest adding bindable events. In particular I would find something like onSpeedZero or onLooping interesting. I imagine:

• onSpeedZero calls callback when the player speed is set to 00 (via F00, I guess), because obviously the song ended.
• onLooping calls callback when the song simply wraps around itself to start from sequence 00.
  I'd like to have these to make a playlist (Add playlist #23).

[a1k0n]

I don't think F00 actually stops the song; speed 0 would be infinitely fast, technically. But yeah, something like that.

[PeterNerlich]

Oh, right. Well I just looked a little bit into downloaded *.xms and stumbled over this effect call stopping playback. I pretty much don't know anything about what does what... :P