rustdoc: refactor: centralize all command-line argument parsing

This is something i've wanted to do for a while, since we keep having to add new arguments to places like `rust_input` or `core::run_core` whenever we add a new CLI flag or the like. Those functions have inflated up to 11-19, and in some cases hiding away the locations where some CLI flags were being parsed, obscuring their use. Now, we have a central place where all command-line configuration occurs, including argument validation.

One note about the design: i grouped together all the arguments that `html::render::run` needed, so that i could pass them on from compilation in one lump instead of trying to thread through individual items or clone the entire blob ahead of time.

One other thing this adds is that rustdoc also now recognizes all the `-Z` options that rustc does, since we were manually grabbing a few previously. Now we parse a full `DebuggingOptions` struct and hand it directly to rustc when scraping docs.

submodules: update clippy from 71ec4ff6 to d8b42690

Fixes clippy toolstate.

Changes:

````
rustup https://github.com/rust-lang/rust/pull/55665 (pass contexts by reference)
Fix typo
Improve clippy_dev help text
RIIR update lints: Generate lint group registrations
Test clippy_dev on CI and fix test
RIIR update lints: Generate modules section
````

Remove checks for LLVM < 4.0

While we still have to support LLVM 4.0 for Emscripten, we can drop checks for LLVM >= 4.0 and < 4.0.

enforce unused-must-use lint in macros

Fixes #55516 by turning on the UNUSED_MUST_USE lint within macros.

Fixes clippy toolstate.

Changes:

````
rustup https://github.com/rust-lang/rust/pull/55665 (pass contexts by reference)
Fix typo
Improve clippy_dev help text
RIIR update lints: Generate lint group registrations
Test clippy_dev on CI and fix test
RIIR update lints: Generate modules section
````

rustc_target: pass contexts by reference, not value.

`LayoutOf` now takes `&self` instead of `self`, and so does every method generic over a context that implements `LayoutOf` and/or other traits, like `HasDataLayout`, `HasTyCtxt`, etc.

Originally using by-value `Copy` types was relevant because `TyCtxt` was one of those types, but now `TyCtxt::layout_of` is separate from `LayoutOf`, and `TyCtxt` is not an often used layout context.

Passing these context by reference is a lot nicer for miri, which has `self: &mut EvalContext`, and needed `f(&self)` (that is, creating `&&mut EvalContext` references) for layout purposes.
Now, the `&mut EvalContext` can be passed to a function expecting `&C`, directly.

This should help with #54012 / #55627 (to not need `where &'a T::Cx: LayoutOf` bounds).

r? @nikomatsakis or @oli-obk or @nagisa cc @sunfishcode

Rename `Value` to `Immediate` for miri

r? @RalfJung

Move collect_and_partition_mono_items to rustc_mir

Most of the logic of it is inside rustc_mir anyway.

Also removes the single function crate rustc_metadata_utils. Based on #55225

single life

 * structured ~~autofixable~~ (well, pending #53934 and rust-lang-nursery/rustfix#141) suggestions for the single-use-lifetimes lint in the case of function and method reference args
 * don't consider the anonymous lifetime `'_` as "single-use" (it's intended for exactly this sort of thing)

![single_life](https://user-images.githubusercontent.com/1076988/47613227-3b2b6400-da48-11e8-8efd-cb975ddf537d.png)

r? @nikomatsakis

Use token description in "expected/found" parse messages

Fix #54309.

rustdoc: Replaces fn main search and extern crate search with proper parsing during doctests.

Fixes #21299.
Fixes #33731.

Let me know if there's any additional changes you'd like made!

submodules: update clippy from a20599ab to 71ec4ff6

Should fix clippy toolstat.

Changes:

````
rustup https://github.com/rust-lang/rust/pull/55330/
Update stderr
Rename test files
Also lint cfg_attr(.., rustfmt::skip)
Add tests from rustfmt::skip test file
Run update_lints.py script
Add test for non-crate-level inner attributes
Differ between inner and outer attributes
Add tests
Add cfg_attr(rustfmt) lint
Addressed comments.
Fix dogfood error.
Added lints `into_iter_on_ref` and `into_iter_on_array`. Fix #1565.
Allow single_match_else
Update stderr
Add copyright statement©
Fix typos
Fix dogfood error
Fix typo and indentation
run update_lints script
Add tests for unknwon_clippy_lints lint
Add new lint: unknwon_clippy_lintsg
clippy: fix pedantic warnings and run clippy::pedantic lints on the codebase.
Fix a false-positive of needless_borrow
UI test cleanup: Extract match_overlapping_arm tests
UI test cleanup: Extract expect_fun_call tests
Add missing code of conduct file
Use slice patterns instead of padding
Fix dogfood and pedantic lints
ci: when installing rust-toolchain-installer-master, install it in debug mode to save some time in ci.
RIIR update lints: Generate deprecated lints
Replace big if/else expression with match
````

Fixed the bug in bootstrap where --exclude was ignored for run-pass test

This should fix the 3 hour timeout on AppVeyor which happened a lot recently.

Additionally, further rebalanced the AppVeyor subsets by moving "ui" and "linkchecker" into Set 2.

Should fix clippy toolstat.

Changes:

````
rustup https://github.com/rust-lang/rust/pull/55330/
Update stderr
Rename test files
Also lint cfg_attr(.., rustfmt::skip)
Add tests from rustfmt::skip test file
Run update_lints.py script
Add test for non-crate-level inner attributes
Differ between inner and outer attributes
Add tests
Add cfg_attr(rustfmt) lint
Addressed comments.
Fix dogfood error.
Added lints `into_iter_on_ref` and `into_iter_on_array`. Fix #1565.
Allow single_match_else
Update stderr
Add copyright statement©
Fix typos
Fix dogfood error
Fix typo and indentation
run update_lints script
Add tests for unknwon_clippy_lints lint
Add new lint: unknwon_clippy_lintsg
clippy: fix pedantic warnings and run clippy::pedantic lints on the codebase.
Fix a false-positive of needless_borrow
UI test cleanup: Extract match_overlapping_arm tests
UI test cleanup: Extract expect_fun_call tests
Add missing code of conduct file
Use slice patterns instead of padding
Fix dogfood and pedantic lints
ci: when installing rust-toolchain-installer-master, install it in debug mode to save some time in ci.
RIIR update lints: Generate deprecated lints
Replace big if/else expression with match
````

This should allow the timings be more balanced.

Fix the recent spurious 3 hour timeouts.

Implement trait aliases (RFC 1733)

Extends groundwork done in https://github.com/rust-lang/rust/pull/45047, and fully implements https://github.com/rust-lang/rfcs/pull/1733.

CC @durka @nikomatsakis

Rollup of 5 pull requests

Successful merges:

 - #54162 (Hide default impls items)
 - #55555 (Make `-Z ls` list the actual filename of external dependencies)
 - #55567 (add test for deriving Debug on uninhabited enum)
 - #55568 (test that rustdoc doesn't overflow on a big enum)
 - #55598 (publish-toolstate: ping maintainers when a tool builds again)

Failed merges:

r? @ghost

Co-Authored-By: Nbjorn3 <bjorn3@users.noreply.github.com>

publish-toolstate: ping maintainers when a tool builds again

And add @Xanewok as an RLS maintainer

r? @kennytm

Motivation is that I see when the RLS gets broken, but have to poll the website to see when it is fixed, I'd prefer to get pinged.

test that rustdoc doesn't overflow on a big enum

Adds a test to close #25295. The test case depended on `enum_primitive` so I just basically pulled its source into an auxiliary file, is that the right way to do it?

add test for deriving Debug on uninhabited enum

Adds a test to close #38885.

Make `-Z ls` list the actual filename of external dependencies

The hash is pointless for external consumers - extra_filename is the thing that actually gets used, per https://github.com/rust-lang/rust/blob/ca2639e/src/librustc_metadata/locator.rs#L312-L313

Hide default impls items

Follow up of #51885.
Fixes #54025.

cc @Mark-Simulacrum

r? @QuietMisdreavus

And screenshots of course:

<img width="1440" alt="screen shot 2018-09-12 at 23 30 35" src="https://user-images.githubusercontent.com/3050060/45454424-1ff8d500-b6e4-11e8-9257-030322495d58.png">

<img width="1440" alt="screen shot 2018-09-12 at 23 30 42" src="https://user-images.githubusercontent.com/3050060/45454431-2424f280-b6e4-11e8-8d65-db0d85ac18f0.png">

Add support for bound types

This PR may have some slight performance impacts, I don't know how hot is the code I touched.

Also, this breaks clippy and miri.

r? @nikomatsakis

Use the new `BoundVarReplacer` to perform canonical substitutions.