update books for the next release

[steveklabnik]

No description provided.

[rust-highfive]

r? @GuillaumeGomez

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[rust-highfive]

Warning

• These commits modify submodules.

[rust-highfive]

The job x86_64-gnu-llvm-3.9 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[01:23:17] travis_fold:end:stage0-linkchecker

[01:23:17] travis_time:end:stage0-linkchecker:start=1525377345213092017,finish=1525377347912520037,duration=2699428020

[01:23:31] reference/items/traits.html:212: broken link fragment `#methods` pointing to `reference/items/functions.html`
[01:23:32] reference/print.html:2110: broken link fragment `#methods` pointing to `reference/items/functions.html`
[01:23:32] reference/print.html:3190: broken link - reference/enumerations.html
[01:23:32] reference/attributes.html:524: broken link - reference/enumerations.html
[01:23:33] thread 'main' panicked at 'found some broken links', tools/linkchecker/main.rs:49:9
[01:23:33] 
[01:23:33] 
[01:23:33] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/linkchecker" "/checkout/obj/build/x86_64-unknown-linux-gnu/doc"
[01:23:33] expected success, got: exit code: 101
[01:23:33] expected success, got: exit code: 101
[01:23:33] 
[01:23:33] 
[01:23:33] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[01:23:33] Build completed unsuccessfully in 0:41:57
[01:23:33] Makefile:58: recipe for target 'check' failed
[01:23:33] make: *** [check] Error 1

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:08f75d00
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[oli-obk]

@bors r+

[bors]

📌 Commit 1ae2668 has been approved by oli-obk

[Mark-Simulacrum]

I believe this will fail in CI without rust-lang/rust-by-example#1077. @bors r-

[frewsxcv]

merged that rust-by-example PR, opened a new rust PR for updating the books here: #50470