Inner attributes don't parse with impls

[nikomatsakis]

struct foo;

impl foo {
    #[cfg(not(test))];

    fn bar() {}
}

fn main() {}

yields

Running /home/nmatsakis/versioned/rust-m/build/i686-unknown-linux-gnu/stage2/bin/rustc:
/home/nmatsakis/tmp/bar.rs:4:21: 4:22 error: unexpected token: `;`
/home/nmatsakis/tmp/bar.rs:4     #[cfg(not(test))];

[huonw]

Dup of #3614.