Inherited traits don't work in trait objects

[Sodel-the-Vociferous]

trait MyTY {
    fn my_y(&self) -> uint;
}

trait MyTXY: MyTY {
    fn my_x(&self) -> uint;
}

fn bar(mt: &MyTXY) {
    mt.my_x();
    mt.my_y();
}

fn main() {
}

[jdm]

Duplicate of #4100.