Rollup merge of rust-lang#79583 - ehuss:update-books, r=ehuss

Update books

## nomicon

1 commits in 23c49f1d5ce4720bc5b7e3a920f47eccc8da6b63..d8383b65f7948c2ca19191b3b4bd709b403aaf45
2020-11-05 13:30:53 +0900 to 2020-11-22 10:24:42 -0500
- Clarify that any alignment is valid for ZSTs

## reference

5 commits in a7de763c213292f5b44bf10acb87ffa38724814d..a8afdca5d0715b2257b6f8b9a032fd4dd7dae855
2020-11-11 19:13:21 -0800 to 2020-11-30 06:44:46 -0800
- Describe relationship between reference and optimizers (rust-lang/reference#902)
- A simple missing space (rust-lang/reference#909)
- Cleanup formatting (rust-lang/reference#907)
- Use `doc`, not `test` for fn item inner attr example (rust-lang/reference#906)
- Update where our chat is. (rust-lang/reference#903)

## book

1 commits in 13e1c05420bca86ecc79e4ba5b6d02de9bd53c62..a190438d77d28041f24da4f6592e287fab073a61
2020-10-20 14:57:32 -0500 to 2020-11-16 10:44:08 -0600
- Change SipHash not found (404) link to SipHash in Wikipedia (rust-lang/book#2503)

## rust-by-example

4 commits in 1886fda6981b723e4de637074455558f8bc1e83c..236c734a2cb323541b3394f98682cb981b9ec086
2020-10-28 13:46:54 -0500 to 2020-11-30 14:05:49 -0300
- Update old invalid link (rust-lang/rust-by-example#1392)
- Moved "See also" link to the correct page. (rust-lang/rust-by-example#1389)
- Fix some markdown lint warnings (rust-lang/rust-by-example#1388)
- Minor grammar suggestion (rust-lang/rust-by-example#1386)

## embedded-book

1 commits in ca8169e69b479f615855d0eece7e318138fcfc00..ba34b8a968f9531d38c4dc4411d5568b7c076bfe
2020-10-15 15:06:35 +0000 to 2020-11-17 00:20:43 +0000
- Clarify CAS availability  (rust-embedded/book#273)