Order of `extern` and `unsafe` is backwards in trait definitions and impls

[ftxqxd]

trait Foo {
    extern "Rust" unsafe fn foo();
}

impl Foo for () {
    extern "Rust" unsafe fn foo() {}
}

unsafe extern "Rust" fn foo() {}

fn main() {}

Here unsafe comes after extern in the Foo’s definition and implementation, but it comes before in the extern in the top-level function foo. I think foo’s order seems the most natural (and would be the most common use anyway), so I would assume that it has the intended order.

[alexcrichton]

Nominating, seems bad.