Rollup merge of rust-lang#90294 - ehuss:update-books, r=ehuss

Update books

## nomicon

3 commits in 2d66852a27c5d0ec50ae021820d1de22caa2b1bd..358e6a61d5f4f0496d0a81e70cdcd25d05307342
2021-10-07 19:00:37 +0900 to 2021-10-20 11:23:12 -0700
- Write a basic "call Rust from C" example (rust-lang/nomicon#296)
- Clarify the Safe vs. Unsafe Rust relationship (rust-lang/nomicon#294)
- Fix typo with respect to dangling pointer (rust-lang/nomicon#319)

## book

8 commits in eb1282ec444db94055fa9531b6f3f803e86bb382..fd9299792852c9a368cb236748781852f75cdac6
2021-09-16 21:17:09 -0400 to 2021-10-22 21:59:46 -0400
- Reword description to emphasize what return does in a match arm
- Correct backwards wording describing From impls. Fixes rust-lang/book#2829
- Remove multiple negatives, add examples. Fixes rust-lang/book#2833
- Fix capitalization in sidebar. Fixes rust-lang/book#2860
- fix quotes
- comments from nostarch and responses for chapter 2
-  (rust-lang/book#2906)
- Merge pull request rust-lang/book#2892 from Enrico2/patch-1

## rust-by-example

1 commits in 9a60624fcad0140826c44389571dc622917cd632..27f1ff5e440ef78828b68ab882b98e1b10d9af32
2021-10-04 08:13:53 -0300 to 2021-10-13 08:04:40 -0300
- Added example of `impl Trait` as an argument (rust-lang/rust-by-example#1468)

## embedded-book

1 commits in 270fccd339e5972d9c900e788f197e81a0bcd956..51739471276b1776dea27cf562b974ef07e24685
2021-10-06 16:28:48 +0000 to 2021-10-17 16:48:42 +0000
- Fix typo in 'The Borrow Checker'  (rust-embedded/book#305)