[Suggestion] More options for .animated sound

[hotdamndel]

First, it's really needed to be available for train objects for some implementations (especially including complex motor sounds which depend not exclusively on speed) since adding many sounds via plugins isn't viable on 3D trains due to plugin sounds playing in cab only.

Also, in some cases sound tempo (=playback speed without pitch change) needs to be varied dynamically similarly to a pitch function, but there's no function for that currently.