Rollup merge of rust-lang#71135 - ehuss:update-books, r=ehuss

Update books

## reference

13 commits in 89dd146..3ce94ca
2020-03-31 09:42:10 -0700 to 2020-04-11 17:00:27 +0200
- UB definition: mention size_of_val for determining a reference's span (rust-lang/reference#793)
- Emphasize that `#[inline]` in all shapes is a hint. (rust-lang/reference#791)
- Added missing comma to Unions reference (rust-lang/reference#790)
- Attributes are now allowed on `if` and `if let` (rust-lang/reference#783)
- `enum`s can now be `#[repr(transparent)]` (rust-lang/reference#741)
- Undocument `use` paths. (rust-lang/reference#665)
- Clarify pub(restricted) a bit (rust-lang/reference#481)
- Add information about || and && to grammar describing `while let`. (rust-lang/reference#772)
- Document the `automatically_derived` attribute. (rust-lang/reference#555)
- Fix unstable check. (rust-lang/reference#743)
- Use common script for link checking. (rust-lang/reference#765)
- Add a basic style guide. (rust-lang/reference#787)
- Size fo empty structs in C is zero byte. (rust-lang/reference#782)

## book

14 commits in c8841f2841a2d26124319ddadd1b6a245f9a1856..f5db319e0b19c22964398d56bc63103d669e1bba
2020-03-22 09:07:01 -0500 to 2020-04-13 08:06:03 -0500
- Update ch01-01-installation.md to require TLS 1.2 (rust-lang/book#2301)
- traits as parameters: Use references instead of moving the values (rust-lang/book#2239)
- Fix a broken link
- Update go docs link (rust-lang/book#2285)
- Add the farsi translation repo link (rust-lang/book#2283)
- Add the missing word to the sentence (ch06-2) (rust-lang/book#2278)
- Fixes hardcoded output (rust-lang/book#2276)
- Use rust-lang/rust linkchecker on CI. (rust-lang/book#2272)
- Add union to the list of keywords (rust-lang/book#2271)
- Clarify the wording (rust-lang/book#2256)
- Improve sentence flow (rust-lang/book#2255)
- Add missing apostrophe (rust-lang/book#2247)
- Update cargo profiles link. (rust-lang/book#2245)
- Add note about chapter 18 in chapter 6 (rust-lang/book#2238)

## rust-by-example

1 commits in a6638463efc7631bc0e8dc67ccd256d4e1b61f1a..c106d1683c3a2b0960f0f0fb01728cbb19807332
2020-04-06 09:39:03 -0500 to 2020-04-09 09:14:39 -0300
- Improve the conversion example (rust-lang/rust-by-example#1329)

## edition-guide

1 commits in 37f9e6848411188a1062ead1bd8ebe4b8aa16899..8204c1d123472cd17f0c1c5c77300ae802eb0271
2020-02-10 14:36:14 +0100 to 2020-04-09 18:55:50 -0700
- Fix forge link. (rust-lang/edition-guide#200)

## embedded-book

1 commits in d22a9c487c78095afc4584f1d9b4ec43529d713c..668fb07b6160b9c468f598e839c1e044db65de30
2020-03-04 09:46:30 +0000 to 2020-04-13 12:38:16 +0000
- Add triagebot configuration  (rust-embedded/book#232)