Auto merge of #75720 - ehuss:update-books, r=ehuss

Update books

## nomicon

2 commits in bfe1ab96d717d1dda50e499b360f2e2f57e1750a..25854752549d44d76fbd7650e17cb4f167a0b8fb
2020-06-05 13:19:42 -0400 to 2020-08-19 16:41:48 -0400
- Follow-up of rust-lang/rust#75152 (rust-lang-nursery/nomicon#235)
- Follow-up for rust-lang/rust#74850 (rust-lang-nursery/nomicon#233)

## reference

7 commits in c9b2736a059469043177e1e4ed41a55d7c63ac28..1b6c4b0afab97c0230433466c97167bbbe8445f6
2020-08-03 03:34:03 -0700 to 2020-08-18 17:04:28 -0700
- Some constant/static updates. (rust-lang-nursery/reference#867)
- Add casting rules from function items to other types (rust-lang-nursery/reference#878)
- Apply joshtriplett's suggestion
- Add note clarifying 16-bit support.
- Document min pointer width.
- Update to `dyn Trait` syntax in a couple places (rust-lang-nursery/reference#875)
- mention that `#[track_caller]` on `fn main` is forbidden (rust-lang-nursery/reference#872)

## book

2 commits in 363293c1c5ce9e84ea3935a5e29ce8624801208a..c0a6a61b8205da14ac955425f74258ffd8ee065d
2020-08-03 15:56:30 -0500 to 2020-08-14 14:21:49 -0500
- Correct listing 11-10: Take tests module out of main function. (rust-lang/book#2427)
- Update link to russian translation (rust-lang/book#2423)

## rust-by-example

5 commits in 2e9271981adc32613365810f3428334c07095215..80a10e22140e28392b99d24ed02f4c6d8cb770a0
2020-07-27 13:39:16 -0500 to 2020-08-08 09:56:46 -0300
- Add tuple `..` operator example (rust-lang/rust-by-example#1368)
- Clarify wording (rust-lang/rust-by-example#1366)
- Include arc (rust-lang/rust-by-example#1365)
- Modify supertraits sample code (rust-lang/rust-by-example#1361)
- Remove mention of `try!` in `Display` example (rust-lang/rust-by-example#1357)

## embedded-book

3 commits in b5256448a2a4c1bec68b93c0847066f92f2ff5a9..0cd2ca116274b915924c3a7e07c1e046b6f19b77
2020-07-24 23:09:29 +0000 to 2020-08-19 10:33:15 +0000
- Ignore unused argument in closure  (rust-embedded/book#261)
- Fix broken sentence  (rust-embedded/book#260)
- Add additional command to try when verifying installation.  (rust-embedded/book#259)