Update verison to 0.42

- Update changelog
- Update some tests
- Fix a nightly warning
- Remove `--crate-type` check for rustdoc.

Update Cargo, books

## cargo

12 commits in 5da4b4d47963868d9878480197581ccbbdaece74..8280633db680dec5bfe1de25156d1a1d53e6d190
2019-10-28 21:53:41 +0000 to 2019-11-11 23:17:05 +0000
- Don't panic when parsing `/proc/stat` (rust-lang/cargo#7580)
- Fix unused configuration key warning for a few keys under `build`. (rust-lang/cargo#7575)
- Add back support for `BROWSER` envvar in `cargo doc --open`. (rust-lang/cargo#7576)
- Only include "already existing ..." comment in gitignore on conflict (rust-lang/cargo#7570)
- Add VS Code user dir to .gitignore (rust-lang/cargo#7578)
- Added aliases to subcommand typo suggestions. (rust-lang/cargo#7486)
- Use multiple requirement syntax consistently (rust-lang/cargo#7573)
- Update verison to 0.42 (rust-lang/cargo#7568)
- Expand documentation on build scripts. (rust-lang/cargo#7565)
- Update crossbeam-utils requirement from 0.6 to 0.7 (rust-lang/cargo#7566)
- don't download std-docs on CI (rust-lang/cargo#7513)
- Change my-buddy to github-handle (rust-lang/cargo#7553)

## nomicon

2 commits in 5004ad30d69f93553ceef74439fea2159d1f769e..58e36e0e08dec5a379ac568827c058e25990d6cd
2019-10-12 19:52:40 +0200 to 2019-10-30 08:14:24 -0500
- remove references to the nursery
- Add github action to replace Travis.yml (rust-lang/nomicon#172)

## reference

7 commits in 4b21b64..45558c4
2019-10-27 22:33:11 +0100 to 2019-11-08 14:47:35 +0100
- Audit code blocks. (rust-lang/reference#715)
- Update coherence and orphan rules documentation to match RFC 2451 (rust-lang/reference#703)
- Update organization name (rust-lang/reference#713)
- State that no_implicit_prelude also applies to nested modules (rust-lang/reference#707)
- expand Copy docs (rust-lang/reference#711)
- github action doesn't use the nursery (rust-lang/reference#706)
- Migrate to GitHub Actions. (rust-lang/reference#705)

## book

1 commits in 28fa3d15b0bc67ea5e79eeff2198e4277fc61baf..e79dd62aa63396714278d484d91d48826737f47f
2019-10-29 07:16:09 -0500 to 2019-10-30 07:33:12 -0500
- No need for an iterator here to fetch values (rust-lang/book#1957)

## rust-by-example

1 commits in f3197ddf2abab9abdbc029def8164f4a748b0d91..dcee312c66267eb5a2f6f1561354003950e29105
2019-10-29 10:17:40 -0300 to 2019-10-31 11:26:53 -0300
- refactor: simplify extracting Result from Option (rust-lang/rust-by-example#1283)

## edition-guide

2 commits in e58bc4ca104e890ac56af846877c874c432a64b5..f553fb26c60c4623ea88a1cfe731eafe0643ce34
2019-07-31 20:14:12 +0200 to 2019-10-30 08:27:42 -0500
- remove old references to the nursery
- Port from Travis to GitHub Actions (rust-lang/edition-guide#192)