Rollup of 9 pull requests

[Centril]

Successful merges:

• Make Layout::new const #66254 (Make Layout::new const)
• Improve code generated for starts_with(<literal char>) #67249 (Improve code generated for starts_with(<literal char>))
• Delete flaky test net::tcp::tests::fast_rebind #67308 (Delete flaky test net::tcp::tests::fast_rebind)
• Improve typeck & lowering docs for slice patterns #67318 (Improve typeck & lowering docs for slice patterns)
• use Self alias in place of macros #67322 (use Self alias in place of macros)
• make transparent enums more ordinary #67323 (make transparent enums more ordinary)
• Fix JS error when loading page with search #67336 (Fix JS error when loading page with search)
• .gitignore: Don't ignore a file that exists in the repository #67344 (.gitignore: Don't ignore a file that exists in the repository)
• Minor: update Unsize docs for dyn syntax #67349 (Minor: update Unsize docs for dyn syntax)

Failed merges:

r? @ghost

[Centril]

@bors r+ p=9 rollup=never

[bors]

📌 Commit 175118f has been approved by Centril

[bors]

🌲 The tree is currently closed for pull requests below priority 100, this pull request will be tested once the tree is reopened

[Centril]

@bors p=200

[rust-highfive]

The job x86_64-gnu-llvm-7 of your PR failed (pretty log, 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.

2019-12-16T15:45:28.9692890Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-12-16T15:45:28.9712364Z ##[command]git config gc.auto 0
2019-12-16T15:45:28.9721782Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-12-16T15:45:28.9733527Z ##[command]git config --get-all http.proxy
2019-12-16T15:45:28.9739416Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/67352/merge:refs/remotes/pull/67352/merge
---
2019-12-16T16:14:41.4184391Z    Compiling backtrace-sys v0.1.32
2019-12-16T16:14:41.5282737Z error: stable const functions must have either `rustc_const_stable` or `rustc_const_unstable` attribute
2019-12-16T16:14:41.5283245Z    --> src/libcore/alloc.rs:122:5
2019-12-16T16:14:41.5283508Z     |
2019-12-16T16:14:41.5283816Z 122 | /     pub const fn new<T>() -> Self {
2019-12-16T16:14:41.5284154Z 123 | |         let (size, align) = size_align::<T>();
2019-12-16T16:14:41.5284518Z 124 | |         // Note that the align is guaranteed by rustc to be a power of two and
2019-12-16T16:14:41.5284891Z 125 | |         // the size+align combo is guaranteed to fit in our address space. As a
2019-12-16T16:14:41.5285430Z 130 | |         }
2019-12-16T16:14:41.5285738Z 131 | |     }
2019-12-16T16:14:41.5285978Z     | |_____^
2019-12-16T16:14:41.5286010Z 
---
2019-12-16T16:14:43.5136752Z   local time: Mon Dec 16 16:14:43 UTC 2019
2019-12-16T16:14:43.8084033Z   network time: Mon, 16 Dec 2019 16:14:43 GMT
2019-12-16T16:14:43.8087878Z == end clock drift check ==
2019-12-16T16:14:46.6389293Z 
2019-12-16T16:14:46.6499357Z ##[error]Bash exited with code '1'.
2019-12-16T16:14:46.6540413Z ##[section]Starting: Checkout
2019-12-16T16:14:46.6564473Z ==============================================================================
2019-12-16T16:14:46.6564536Z Task         : Get sources
2019-12-16T16:14:46.6564592Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

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