Outlives obligations aren't normalized before processing

This code should compile:

```rust
trait Tr<'a> {
    type Assoc;
}

fn outlives<'o, T: 'o>() {}

fn foo<'a, 'b, T: Tr<'a, Assoc = ()>>() {
    outlives::<'b, T::Assoc>();
}
```

Similar to #59, but in the other direction (should pass, but fails).