dead-code lint: say "constructed" for structs

Respectively.

This is a sequel to November 2017's #46103 / 1a9dc2e9. It had been
reported (more than once—at least #19140, #44083, and #44565) that the
"never used" language was confusing for enum variants that were "used"
as match patterns, so the wording was changed to say never "constructed"
specifically for enum variants. More recently, the same issue was raised
for structs (#52325). It seems consistent to say "constructed" here,
too, for the same reasons.

~~While we're here, we can also use more specific word "called" for unused
functions and methods. (We declined to do this in #46103, but the
rationale given in the commit message doesn't actually make sense.)~~

This resolves #52325.

make `everybody_loops` preserve item declarations

First half of https://github.com/rust-lang/rust/issues/52545.

`everybody_loops` is used by rustdoc to ensure we don't contain erroneous references to platform APIs if one of its uses is pulled in by `#[doc(cfg)]`. However, you can also implement traits for public types inside of functions. This is used by Diesel (probably others, but they were the example that was reported) to get around a recent macro hygiene fix, which has caused their crate to fail to document. While this won't make the traits show up in documentation (that step comes later), it will at least allow files to be generated.

data_structures: make TinyList more readable and optimize remove(_)

also add benchmarks

Before:

```
test tiny_list::test::bench_insert_empty             ... bench:           1 ns/iter (+/- 0)
test tiny_list::test::bench_insert_one               ... bench:          16 ns/iter (+/- 0)
test tiny_list::test::bench_remove_empty             ... bench:           2 ns/iter (+/- 0)
test tiny_list::test::bench_remove_one               ... bench:           6 ns/iter (+/- 0)
test tiny_list::test::bench_remove_unknown           ... bench:           4 ns/iter (+/- 0)
```

After:

```
test tiny_list::test::bench_insert_empty             ... bench:           1 ns/iter (+/- 0)
test tiny_list::test::bench_insert_one               ... bench:          16 ns/iter (+/- 0)
test tiny_list::test::bench_remove_empty             ... bench:           0 ns/iter (+/- 0)
test tiny_list::test::bench_remove_one               ... bench:           3 ns/iter (+/- 0)
test tiny_list::test::bench_remove_unknown           ... bench:           2 ns/iter (+/- 0)
```

rustdoc: refactor how passes are structured, and turn intra-doc-link collection into a pass

This builds on https://github.com/rust-lang/rust/pull/52751 and should not be merged until that finally finishes the bors queue

Part 2 of my passes refactor. This introduces the concept of an "early pass", which is run right before exiting the compiler context. This is important for passes that may want to ask the compiler about things. For example, i took out the intra-doc-link collection and turned it into a early pass. I also made the `strip-hidden`, `strip-private` and `strip-priv-imports` passes occur as early passes, so that intra-doc-link collection wouldn't run on docs that weren't getting printed.

Fixes https://github.com/rust-lang/rust/issues/51684, technically https://github.com/rust-lang/rust/issues/51468 too but that version of `h2` hits a legit intra-link error after that `>_>`

r? @rust-lang/rustdoc

Update LLVM submodule to 7.0

This commit updates the following submodules to LLVM's [recently branched][1]
7.0 release branch:

* src/llvm
* src/tools/lld
* src/libcompiler_builtins/compiler-rt

[1]: https://lists.llvm.org/pipermail/llvm-dev/2018-August/125004.html

Closes #52970

[NLL] Use smaller spans for errors involving closure captures

Closes #51170
Closes #46599

Error messages involving closures now point to the captured variable/closure args.

r? @pnkfelix

avoid computing liveness for locals that escape into statics

Fixes #52713

I poked at this on the plane and I think it's working -- but I want to do a bit more investigation and double check. The idea is to identify those local variables where the entire value will "escape" into the return -- for them, we don't need to compute liveness, since we know that the outlives relations from the return type will force those regions to be equal to free regions. This should help with html5ever in particular.

- [x] test performance
- [x] verify correctness
- [x] add comments

r? @pnkfelix
cc @lqd

Update cargo to fix Rust 2018 build scripts

This commit updates the following submodules to LLVM's [recently branched][1]
7.0 release branch:

* src/llvm
* src/tools/lld
* src/libcompiler_builtins/compiler-rt

[1]: https://lists.llvm.org/pipermail/llvm-dev/2018-August/125004.html

Closes #52970

Update rustfmt, RLS, Clippy

r? @kennytm

Fixes RLS build and updates RLS and Rustfmt to their 1.0 RCs

rustdoc: clean up generic impls

r? @QuietMisdreavus

Cleanup for librustc::session

Some rather straightforward cleanup. Each commit mostly stands alone.

Rollup of 14 pull requests

Successful merges:

 - #51919 (Provide `{to,from}_{ne,le,be}_bytes` functions on integers)
 - #52940 (Align 6-week cycle check with beta promotion instead of stable release.)
 - #52968 (App-lint-cability)
 - #52969 (rustbuild: fix local_rebuild)
 - #52995 (Remove unnecessary local in await! generator)
 - #52996 (RELEASES.md: fix the `hash_map::Entry::or_default` link)
 - #53001 (privacy: Fix an ICE in `path_is_private_type`)
 - #53003 (Stabilize --color and --error-format options in rustdoc)
 - #53022 (volatile operations docs: clarify that this does not help wrt. concurrency)
 - #53024 (Specify reentrancy gurantees of `Once::call_once`)
 - #53041 (Fix invalid code css rule)
 - #53047 (Make entire row of doc search results clickable)
 - #53050 (Make left column of rustdoc search results narrower)
 - #53062 (Remove redundant field names in structs)

Remove redundant field names in structs

This is a clippy-breaking change.