Weird "use of undeclared lifetime" with foreign function

``` rust
extern {
   pub fn life<'a>(x:&'a i32);
}
fn main() {}
```

```
<anon>:2:23: 2:25 error: use of undeclared lifetime name `'a` [E0261]
<anon>:2    pub fn life<'a>(x:&'a i32);
                               ^~
error: aborting due to previous error
playpen: application terminated with error code 101
```
