Second pass of name resolution

[vorner]

Hello

I found a bit of more time for the name resolution (#16) and put some more stuff there.

However, I'm afraid the whole chapter is above my abilities (or time, at least) to document reasonably ‒ I'm reading through the code and still don't understand most of it and have no idea about which part of code relates to the other bullet points in the issue description. Therefore, if there's someone else who might want to have a look at it, I'd like to release the lock on the task and I'll find some other way to contribute to rust (pull requests to random crates I use seem to have better cost-effect ratio for me).

[mark-i-m]

Thanks @vorner!

[mark-i-m]

If you want, there are a bunch of other issues on this repo that may have lower time commitments: https://github.com/rust-lang-nursery/rustc-guide/labels/help%20wanted

(Of course, please don't feel obligated in any way!)

If it helps:

• There's also usually a "Help wanted" section in https://this-week-in-rust.org

• And there are also sometimes mentored issues in the rust repo itself.