I don't think this is correct, it's very unlikely that we want

```rust
#[macro_escape]
fn foo() {
    macro_rules! bar( () => { 1 } )
}

fn bar() -> int {
    bar!()
}
```
to work.

I think just calling `noop_fold_item` here without `macro_escape` or `with_exts_frame` should be fine.