Implement Interface Using Super

[Jonathan Levi]

This works in LDC but not DMD?

```
class A : B, I {
     alias i = typeof(super).i;
}
class B {
     void i() {
         writeln("i");
     }
}
interface I {
     void i();
}
```

Is this a bug in DMD or in LDC?  How can I get this effect 
correctly?