[beta] Rollup backports

[emilyalbini]

PRs accepted for backport:

• Update LLVM submodule #56781: Update LLVM submodule
• Update the book to fix some edition-related bugs #56615: Update the book to fix some edition-related bugs
• Update libc version required by rustc #56562: Update libc version required by rustc
• Fix #56237: normalize type before deferred sizedness checking. #56282: Fix Inference regression in nightly affecting Pin::set and futures #56237: normalize type before deferred sizedness checking.
• Release notes for Rust 1.31.1

Approved PRs targeting beta:

• [beta] rustdoc: fix line numbers display for [src] pages #56819: [beta] rustdoc: fix line numbers display for [src] pages
• [beta] Revert "Update CI-clang to 7.0.0 for Linux dists." #56893: [beta] Revert "Update CI-clang to 7.0.0 for Linux dists."

r? @ghost

[emilyalbini]

@bors r+ p=10

[bors]

📌 Commit 9d49d7d has been approved by pietroalbini

[emilyalbini]

@bors r+ p=10

[bors]

📌 Commit f31a768 has been approved by pietroalbini

[bors]

⌛ Testing commit f31a768 with merge f08b90adaa4b785195c25693e2ef44063847d3e7...

[bors]

💔 Test failed - status-travis

[rust-highfive]

The job dist-x86_64-linux-alt 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.

[02:58:49] travis_time:end:stage2-cargo-clippy:start=1545110229051512549,finish=1545110229418503360,duration=366990811

[02:58:49] [TIMING] ToolBuild { compiler: Compiler { stage: 2, host: "x86_64-unknown-linux-gnu" }, target: "x86_64-unknown-linux-gnu", tool: "cargo-clippy", path: "src/tools/clippy", mode: ToolRustc, is_optional_tool: true, source_type: Submodule, extra_features: [] } -- 0.380
[02:58:53] [TIMING] Clippy { stage: 2, target: "x86_64-unknown-linux-gnu" } -- 3.683
The job exceeded the maximum time limit for jobs, and has been terminated.

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)

[kennytm]

@bors retry

3 hour timeout?

[bors]

⌛ Testing commit f31a768 with merge a1b9cf6...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: pietroalbini
Pushing a1b9cf6 to beta...