Links to types in an extern crate declared somewhere other than the crate root are broken

[sfackler]

See for example SslStream on this page: http://sfackler.github.io/rust-postgres/doc/v0.10.1/postgres/io/trait.StreamWrapper.html

The link has an /io/openssl/ in it that shouldn't be there.

[mitaa]

I'm pretty sure this broke with #27458, which invalidates the assumption that the local path is eqivalent to the extern path.

https://github.com/rust-lang/rust/blob/master/src/librustdoc/clean/inline.rs#L134-L147