* Store the local crates in an Rc<[CrateNum]>
* Move all the allocation history into Stacks
* Clean up the implementation of get_logs_relevant_to a bit
* Pass a ThreadInfo down to grant/access to get the current span lazily
* Rename add_* to log_* for clarity
* Hoist borrow_mut calls out of loops by tweaking the for_each signature
* Explain the parameters of check_protector a bit more