resolve: Add regression tests for fixed issues

This adds regression tests for fixed issues in resolve (closes #22146, closes #24883, closes #26930).
r? @EddyB

Review fixes for #32878

This contains review fixes for the PR.

Set the version number for stabilization of braced_empty_structs

and augmented_assignment to 1.8.0.

Per the comments, the numbers in this table reflect the "current
status".

cc @rust-lang/libs @rust-lang/lang

Discovered this while hunting for 1.8 features. I'm afraid there may be more of these that are incorrect and we may have created a mess.

Blacklist fn item types from being used with variadic functions.

Fixes #32201 by adding fn types to the variadic blacklist which currently includes `bool`, `i8`, `u8`, `i16`, `u16` and `f32`.

Fix cargotest

Tested in dev.

Use crate name/disambiguator instead of SVH for debuginfo typeid.

rustdoc: Remove the json-{input, output} format

(for reference #32698)

fixes #25108

r? @alexcrichton

rustbuild: Support cross rust-docs packages

Right now if you configure multiple hosts rustbuild will only build
documentation for the build triple, but we've got all the support necessary to
build documentation for different architectures as well. This commit
reinterprets the `target` field of doc `Step` instances to be the target of the
documentation rather than the target of the rustdoc/tool being run.

This should enable `make dist` to start producing a bunch of `rust-docs`
packages for all the cross architectures that rustbuild is producing now.

Release notes for 1.8

cc @steveklabnik to me the highlights are compound assignment overloading, 32-bit MSVC builds being ready for use, and the cargo improvements.

[Rendered](https://github.com/brson/rust/blob/relnotes/RELEASES.md).

Handle operand temps for function calls

Previously, all non-void function returns required an on-stack location for the value to be stored to. This code improves translation of function calls so this is no longer necessary.

Drop the default buffer size to 8K

The 64k capacity was picked by me a couple of years ago in the initial
implementation of buffered IO adaptors:
https://github.com/rust-lang/rust/pull/9091/files#diff-b131eeef531ad098b32f49695a031008R62.
64K was picked for symmetry with libuv, which we no longer use.

64K is *way* larger than the default size of any other language that I
can find. C, C++, and Java default to 8K, and Go defaults to 4K. There
have been a variety of issues filed relating to this such as #31885.

Closes #31885

Some types weren't being properly monomorphised, and didn't have their
regions properly erased. This is now fixed.

Also fixes an issue where a temp was initialized in two separate
branches, but wasn't given an alloca.

Rollup of 7 pull requests

- Successful merges: #32687, #32729, #32731, #32732, #32734, #32737, #32741
- Failed merges:

and augmented_assignment to 1.8.0.

Per the comments, the numbers in this table reflect the "current
status".

Remove strange names created by lack of privacy-conscious name lookup

The fixed issue that allowed this was #12808.

Fix backtraces on ARM EHABI.

Before this patch, our `rust_eh_personality_catch` routine would cut
backtracing short at the `__rust_try` function, due to it not handling
the `_US_FORCE_UNWIND` bit properly, which is passed by libunwind
implementations on ARM EHABI.

Examples of where the `_US_FORCE_UNWIND` bit is passed to the PR:
- GCC's libunwind: https://github.com/gcc-mirror/gcc/blob/f1717362de1e56fe1ffab540289d7d0c6ed48b20/libgcc/unwind-arm-common.inc#L590
- LLVM's libunwind: https://github.com/llvm-mirror/libunwind/blob/61278584b5c84c422ff5da10f46c3235c54636c9/src/UnwindLevel1-gcc-ext.c#L153

Use DWARF 5 value for DW_LANG_Rust

DWARF 5 has assigned a value for `DW_LANG_Rust`.  See [the relevant DWARF issue](http://www.dwarfstd.org/ShowIssue.php?issue=140129.1).  Although DWARF 5 is not yet released, it seems ok to use this value as both GCC and LLVM are already using other `DW_LANG_` constants assigned in this way.

Handle integer-extending for C ABI

We need to supply sext/zext attributes to LLVM to ensure that arguments
are extended to the appropriate width in the correct way.

Most platforms extend integers less than 32 bits, though not all.

mk: Hardcode the bootstrap key for each release

Starting with the 1.10.0 release we would like to bootstrap all compilers from
the previous stable release. For example the 1.10.0 compiler should bootstrap
from the literal 1.9.0 release artifacts. To do this, however, we need a way to
enable unstable features temporarily in a stable compiler (as the released
compiler is stable), but it turns out we already have a way to do that!

At compile time the configure script selects a `CFG_BOOTSTRAP_KEY` variable
value and then exports it into the makefiles. If the `RUSTC_BOOTSTRAP_KEY`
environment variable is set to this value, then the compiler is allowed to
"cheat" and use unstable features.

This method of choosing the bootstrap key, however, is problematic for the
intention of bootstrapping from the previous release. Each time a 1.9.0 compiler
is created, a new bootstrap key will be selected. That means that the 1.10.0
compiler will only compile from *our* literal release artifacts. Instead
distributions would like to bootstrap from their own compilers, so instead we
simply hardcode the bootstrap key for each release.

This patch uses the same `CFG_FILENAME_EXTRA` value (a hash of the release
string) as the bootstrap key. Consequently all 1.9.0 compilers, no matter where
they are compiled, will have the same bootstrap key. Additionally we won't need
to keep updating this as it'll be based on the release number anyway.

Once the 1.9.0 beta has been created, we can update the 1.10.0 nightly sources
(the `master` branch at that time) to bootstrap from that release using this
hard-coded bootstrap key. We will likely just hardcode into the makefiles what
the previous bootstrap key was and we'll change that whenever the stage0
compiler is updated.

Change build helper to modify suffix

The current implementation of [gcc](https://crates.io/crates/gcc) defaults to using the ```CC``` environment variable to determine the compiler. The current global-find-replace in ```build_helper``` causes issues for projects using tools like ```ccache``` if they try to integrate libstd into their build system.

Almost all cross-compiler toolchains have the tool name as a suffix of the filename, so changing this to suffix-replacement instead of global-replacement should be fine.

Fix libstd on DragonFly

Following changes:

* birthtime does not exist on DragonFly
* errno: __dfly_error is no more. Use #[thread_local] static errno.
* clock_gettime expects a c_ulong

These changes are required to build DragonFly snapshots again.

Save/load incremental compilation dep graph

Contains the code to serialize/deserialize the dep graph to disk between executions. We also hash the item contents and compare to the new hashes. Also includes a unit test harness. There are definitely some known limitations, such as https://github.com/rust-lang/rust/issues/32014 and https://github.com/rust-lang/rust/issues/32015, but I am leaving those for follow-up work.

Note that this PR builds on https://github.com/rust-lang/rust/pull/32007, so the overlapping commits can be excluded from review.

r? @michaelwoerister

Rollup of 7 pull requests

- Successful merges: #32674, #32699, #32711, #32745, #32748, #32757, #32789
- Failed merges:

resolve: Avoid emitting redundant path resolution errors

This PR avoids emitting redundant path resolution errors in `resolve` (fixes #32760).

r? @EddyB

Fix typos in atomic compare_exchange.

Failure ordering can't be Release, not (not) Acquire. Seems like a typo copy-pasted all over.

Reinstate fast_reject for overlap checking

The initial implementation of specialization did not use the
`fast_reject` mechanism when checking for overlap, which caused a
serious performance regression in some cases.

This commit modifies the specialization graph to use simplified types
for fast rejection when possible, and along the way refactors the logic
for building the specialization graph.

Closes #32499

r? @nikomatsakis

Fix infinite loop in Arc::downgrade

Specialize equality for [T] and comparison for [u8] to use memcmp when possible

Specialize equality for [T] and comparison for [u8] to use memcmp when possible

Where T is a type that can be compared for equality bytewise, we can use
memcmp. We can also use memcmp for PartialOrd, Ord for [u8].

Use specialization to call memcmp in PartialEq for slices for certain element types. This PR does not change the user visible API since the implementation uses an intermediate trait. See commit messages for more information.

The memcmp signature was changed from `*const i8` to `*const u8` which is in line with how the memcmp function is defined in C (taking const void * arguments, interpreting the values as unsigned bytes for purposes of the comparison).

Lay groundwork for RFC 1422  and improve `PrivateItemsInPublicInterfacesVisitor`

This PR lays groundwork for RFC 1422 (cc #32409) and improves `PrivateItemsInPublicInterfacesVisitor`. More specifically, it
 - Refactors away `hir::Visibility::inherit_from`, the semantics of which are obsolete.
 - Makes `hir::Visibility` non-`Copy` so that we will be able to add new variants to represent `pub(restricted)` (for example, `Visibility::Restricted(Path)`).
 - Adds a new `Copy` type `ty::Visibility` that represents a visibility value, i.e. a characterization of where an item is accessible. This is able to represent `pub(restricted)` visibilities.
 - Improves `PrivateItemsInPublicInterfacesVisitor` so that it checks for items in an interface that are less visible than the interface. This fixes #30079 but doesn't change any other behavior.

r? @nikomatsakis

Suggest adding a where-clause when that can help

Suggest adding a where-clause when there is an unmet trait-bound that can be satisfied if some type can implement it.

r? @nikomatsakis