After a hash mismatch error, emit file-system paths of crates involved.

Fix #13266.

There is a little bit of acrobatics in the definition of `crate_paths`
to avoid calling `clone()` on the dylib/rlib unless we actually are
going to need them.

The other oddity is that I have replaced the `root_ident: Option<&str>`
parameter with a `root: &Option<CratePaths>`, which may surprise one
who was expecting to see something like: `root: Option<&CratePaths>`.
I went with the approach here because I could not come up with code for
the alternative that was acceptable to the borrow checker.
rustdoc: Fix reporting of ignored tests

librustdoc: instead of skipping ignored tests, pass them to libtest
so it can report them as such.  If a test is marked as `notrust`,
however, it will not show up in the final report.
[std::cmp] add missing docs and provide an example
auto merge of #12956 : killerswan/rust/docs, r=alexcrichton
auto merge of #13272 : ipetkov/rust/rustdoc-ignored-tests, r=alexcrichton

librustdoc: instead of skipping ignored tests, pass them to libtest
so it can report them as such.  If a test is marked as `notrust`,
however, it will not show up in the final report.

Fix #12939
Update README.md

Fix typo
Fix inner attribute syntax from `#[foo];` to `#![foo]`

From the 0.10 changelog:
 * The inner attribute syntax has changed from `#[foo];` to `#![foo]`.
Add stdlib docs to the Linux binary tarball.

These are not installed anywhere, but are included under `./doc` for
those who want an offline copy with their nightlies. This increases the
size of the (compressed) tarball from 76 to 83 MB.
syntax: remove obsolete mutability from ExprVec and ExprRepeat.
std: TrieSet should implement container::{,Mutable}Set
extra: Add with_capacity to PriorityQueue and SmallIntMap
Register new snapshots
Added grow_fn and retain to Vec
Test fixes from rollup
auto merge of #13326 : alexcrichton/rust/rollup, r=alexcrichton

Closes #13313 (Fix typo in README.md)
Closes #13311 (Fix inner attribute syntax from `#[foo];` to `#![foo]`)
Closes #13309 (Add stdlib docs to the Linux binary tarball.)
Closes #13308 (syntax: remove obsolete mutability from ExprVec and ExprRepeat.)
Closes #13306 (TrieSet should impl Set/MutableSet; add with_capacity to PriorityQueue/SmallIntMap)
Closes #13303 (Register new snapshots)
Closes #13274 (Added grow_fn and retain to Vec)

*Issues Closed*

Closes #13249
Small change to example to make variable values more sensible.
Removed all instance of `@` in code examples.
rustc: move the check_loop pass earlier.

This pass is purely AST based, and by running it earlier we emit more
useful error messages, e.g. type inference fails in the case of `let r =
break;` with few constraints on `r`, but its more useful to be told that
the `break` is outside a loop (rather than a type error) when it is.

Closes #13292.
Removed cmath and instrinsic wrapper.
Remove references to obsolete `do` keyword

Also add the new `proc` keyword to the documentation.