Rollup merge of rust-lang#72592 - ehuss:update-books, r=ehuss

Update books

## reference

7 commits in 892b928b565e35d25b6f9c47faee03b94bc41489..becdca9477c9eafa96a4eea5156fe7a2730d9dd2
2020-05-11 11:13:51 -0700 to 2020-05-21 21:08:02 +0100
- Update tuple index token. (rust-lang/reference#814)
- Fixes minor errors (rust-lang/reference#818)
- Update that macros can be deprecated. (rust-lang/reference#813)
- work on char/str descriptions (rust-lang/reference#809)
- cfg_attr needs a valid predicate (rust-lang/reference#812)
- Account for removal of UB in float-to-int casts (rust-lang/reference#810)
- Fix stray plus signs. (rust-lang/reference#811)

## book

6 commits in 6247be15a7f7509559f7981ee2209b9e0cc121df..e8a4714a9d8a6136a59b8e63544e149683876e36
2020-05-03 10:55:09 -0500 to 2020-05-25 10:29:27 -0500
- code is 1024 now, not 512
- Clean up install a bit
- We don't need build.sh anymore
- Fix CI status in README
- Port to github actions (rust-lang/book#2337)
- operating system -> allocator

## rust-by-example

5 commits in ab072b14393cbd9e8a1d1d75879bf51e27217bbb..7aa82129aa23e7e181efbeb8da03a2a897ef6afc
2020-05-09 08:46:39 -0300 to 2020-05-25 14:54:26 -0300
- Person of age 0 is alive (rust-lang/rust-by-example#1348)
- Gramatical fix in std/rc.md (rust-lang/rust-by-example#1347)
- Capture example should use String (rust-lang/rust-by-example#1331)
- Fix empty bound examples (rust-lang/rust-by-example#1343)
- Fix an inline comment in macros/repeat.md (rust-lang/rust-by-example#1344)

## edition-guide

1 commits in 49270740c7a4bff2763e6bc730b191d45b7d5167..0a8ab5046829733eb03df0738c4fafaa9b36b348
2020-05-11 08:50:29 -0500 to 2020-05-18 08:34:23 -0500
- Changes for Rust 1.32 & setup for edition-next (rust-lang/edition-guide#213)

## embedded-book

3 commits in 366c50a03bed928589771eba8a6f18e0c0c01d23..5555a97f04ad7974ac6fb8fb47c267c4274adf4a
2020-05-07 09:04:42 +0000 to 2020-05-25 18:00:51 +0000
- Remove reference to const-fn feature of cortex-m. Closes rust-embedded/book#242.  (rust-embedded/book#243)
- Spelling: Appplication -> Application  (rust-embedded/book#241)
- QEMU debugging updates  (rust-embedded/book#239)

Author: Dylan-DPC