bar_width during control

[Honktown]

A progressbar element cannot have the bar_width changed in control. This precludes scaling existing bars, or having many bars at different scale without creating prototypes for each.

[Klonan]

Surprisingly, this is already 95% implemented in LuaStyle, it is just missing the binding to actually set it, so it should be ridiculously easy to add

[Bilka]

This was added in 1.1.47.