Auto merge of #1158 - divergentdave:shim-rename, r=RalfJung

Add shim for rename

This adds a straightforward shim for rename, which is used by `std::fs::rename`. Testing is included.

As a heads up, I expect one or two merge conflicts between my PRs, since some of them touch the same `use` statements, or add items near the same places. I'll rebase and fix them as they come up.

diff --cc src/shims/foreign_items.rs
Simple merge