Rust update: no more `[T, ..n]` -> `&[T]` coercion
De-mod-ify some stuff enum scoping makes possible

Not strictly necessary, but fun, and it fixes a warning.
I also improved it a little while I was at it.
What can I say? It just happened.
Fix an unused result error.
Use proper Cargo build support.

This gives proper Windows support.
Rust update: no more `[T, ..n]` -> `&[T]` coercion

(I had managed to miss the tests.)
Merge branch 'master' of github.com:chris-morgan/rust-http
Fix missed coercion in the docs