Rollup merge of rust-lang#59754 - ehuss:update-books, r=frewsxcv

Update books

## nomicon

1 commits in f1ff93b66844493a7b03101c7df66ac958c62418..c02e0e7754a76886e55b976a3a4fac20100cd35d
2019-02-26 13:37:28 -0500 to 2019-03-25 16:52:56 -0400
- dropck: The drop order is now defined (rust-lang/nomicon#113)

## reference

3 commits in 27ad493..98f90ff
2019-03-26 02:06:15 +0100 to 2019-04-06 09:29:08 -0700
- Document repr packed(N). (rust-lang/reference#553)
- Fix broken link in glossary. (rust-lang/reference#558)
- Typo fixes (rust-lang/reference#556)

## embedded-book

2 commits in 07fd3880ea0874d82b1d9ed30ad3427ec98b4e8a..7989c723607ef5b13b57208022259e6c771e11d0
2019-03-27 15:40:52 +0000 to 2019-04-04 12:14:37 +0000
- fix rust-embedded/book#182  (rust-embedded/book#183)
- Add openocd to list of installable packages  (rust-embedded/book#179)