Function b2MakeRoundedBox 

pub unsafe extern "C" fn b2MakeRoundedBox(
    halfWidth: f32,
    halfHeight: f32,
    radius: f32,
) -> b2Polygon

Make a rounded box, bypassing the need for a convex hull. @param halfWidth the half-width (x-axis) @param halfHeight the half-height (y-axis) @param radius the radius of the rounded extension