This commit makes the JSON emitter use `-Z terminal-width` in the
"rendered" field of the JSON output.

Signed-off-by: David Wood <david@davidtw.co>

…atch, r=oli-obk

Stabilize `#![feature(const_if_match)]`

Quoting from the [stabilization report](rust-lang#49146 (comment)):

> `if` and `match` expressions as well as the short-circuiting logic operators `&&` and `||` will become legal in all [const contexts](https://doc.rust-lang.org/reference/const_eval.html#const-context). A const context is any of the following:
>
> - The initializer of a `const`, `static`, `static mut` or enum discriminant.
> - The body of a `const fn`.
> - The value of a const generic (nightly only).
> - The length of an array type (`[u8; 3]`) or an array repeat expression (`[0u8; 3]`).
>
> Furthermore, the short-circuiting logic operators will no longer be lowered to their bitwise equivalents (`&` and `|` respectively) in `const` and `static` initializers (see rust-lang#57175). As a result, `let` bindings can be used alongside short-circuiting logic in those initializers.

Resolves rust-lang#49146.

Ideally, we would resolve 🐳 rust-lang#66753 before this lands on stable, so it might be worth pushing this back a release. Also, this means we should get the process started for rust-lang#52000, otherwise people will have no recourse except recursion for iterative `const fn`.

r? @oli-obk

Added io forwarding methods to the stdio structs

Added methods to forward the `io::Read` and `io::Write` methods of the myriad wrapper structs in `stdio.rs` to their underlying readers / writers. This is especially important for the structs on the outside of a locking boundary, to ensure that the lock isn't being dropped and re-acquired in a loop.

…Amanieu

Add documentation to point to `File::open` or `OpenOptions::open` instead of `is_file` to check read/write possibility

Fixes rust-lang#64170.

This adds documentation to point user towards `!is_dir` instead of `is_file` when all they want to is read from a source.

I ran `rg "fn is_file\("` to find all `is_file` methods, I hope I did not miss one.

Prepare for LLVM 11

These are just the code changes needed to build with the current LLVM master (version 11).

r? @nikic

…er, r=estebank

errors: use `-Z terminal-width` in JSON emitter

This PR makes the JSON emitter use `-Z terminal-width` in the "rendered" field of the JSON output.

r? @estebank

replace more `DefId`s with `LocalDefId`

part of rust-lang#70853

fix typo in self-profile.md