Arced bar controls are not supported

[wixoaGit]

https://www.byond.com/docs/ref/skinparams.html

A bar that can be used to show progress, health level, magic level, etc., or used as an adjustable slider. The bar can be straight or formed into an arc. Any area not covered by the bar or slider is transparent, so you can make an arc around another control.

We currently support straight bars, but not arced ones.

[amylizzle]

Fixed by #1375 (though arc functionality is not implemented)