…ONTRIBUTING

Upgrade comment to doc comment.

Also fixes some stdlib links to the reference which have changed.

some dataflow-tracked borrow-data entry.

Fix rust-lang#44828

(The comment thread on the aforementioned issue discusses why its best
to just remove this assertion.)

…veklabnik

Corrected the CONTRIBUTING.md "External Dependencies" section

The "External Dependencies" section is a little outdated.
Please see following comments rust-lang#44567 (comment) rust-lang#44567 (comment) for rationale.

Add links to headers in README and CONTRIBUTING

this also adds dependencies to CONTRIBUTING

I'm just getting started building the rust compiler and noticed this information/ability was missing.

It was also missing the gdb dependency for running tests. I pulled the information out of `appveyor.yml` and recommended later than 7.1 because that is what [apt ships](https://packages.ubuntu.com/search?suite=trusty&keywords=gdb). Feel free to tell me something different!

fix ItemKind::DefaultImpl doc comment

Upgrade comment to doc comment.

...Is this actually used? If so, why does the `Impl` variant right below have a `Defaultness`?

update books for next release

Also fixes some stdlib links to the reference which have changed.

First step in https://forge.rust-lang.org/release-process.html, doing it a few days early 😄

…exes-ice, r=arielb1

`EndRegion` do not always correspond to borrow-data entries

Remove assertion that the argument to every `EndRegion` correspond to some dataflow-tracked borrow-data entry.

Fix rust-lang#44828

(The comment thread on the aforementioned issue discusses why its best to just remove this assertion.)

Use HTTPS protocol for "chat.mibbit.com"

I changed the `http://` protocol to `https://` for the `chat.mibbit.com` website. 📝

--[**Suriyaa**](https://mozillians.org/de/u/suriyaakudo/) 🦊

(*PS: Is somebody interested to vouch me at https://mozillians.org/de/u/suriyaakudo/?*)

Typo in `librustc/README.md`

Add missing urls for Mutex

r? @rust-lang/docs

…m, r=pnkfelix

add the issue number to doc_masked's feature gate

Whoops, missed this in the original `#[doc(masked)]` PR.