Refactored PlaybackHelper into CustomSdlMixerEffectHandler. Otherrefact.
Refactored PlaybackHelper into CustomSdlMixerEffectHandler. Otherrefact.

Also moved the callback code to CustomSdlMixerEffectHandler and added
callbacks (as static methods) that call methods.
hydren/fgeal,hydren/fgeal,hydren/fgeal