…d elements.

Remove a useless test

…-DPC

Replace .unwrap() with ? in std::os::unix::net

As people like to copy examples, this gives them good habits.

…r=oli-obk

rustc: move mir::SourceScopeLocalData to a field of SourceScopeData.

By having one `ClearCrossCrate<SourceScopeLocalData>` for each scope, as opposed to a single `ClearCrossCrate` for all the `SourceScopeLocalData`s, we can represent the fact that some scopes have `SourceScopeLocalData` associated with them, and some don't.

This is useful when doing MIR inlining across crates, because the `ClearCrossCrate` will be `Clear` for the cross-crate MIR scopes and `Set` for the local ones.

Also see rust-lang#66203 (comment) for some context around this approach.

Fixes rust-lang#51314.

rustc: hide HirId's fmt::Debug output from -Z span_free_formats.

This replaces the only occurrences of `HirId {...}` from tests with paths, i.e.:
```rust
[closure@HirId { owner: DefIndex(4), local_id: 15 } q:&i32, t:&T]
```
becomes, after this PR:
```rust
[closure@foo<T>::{{closure}}#0 q:&i32, t:&T]
```

r? @oli-obk cc @michaelwoerister

rustc_plugin: Remove some remaining plugin features

- Plugin arguments (`#![plugin(my_plugin(args))]`) are no longer supported.
- Registering additional plugins from command line (`-Z extra-plugins=my_plugin`) is no longer supported, `-Z crate-attr=plugin(my_plugin)` can be used instead.
- Lint `plugin_as_library` is removed as mostly useless now, when plugins exist as a compatibility feature with greatly reduced functionality.
- Plugins registering additional LLVM passes (`Registry::register_llvm_pass`) are no longer supported, `-C                   passes=my_passes` can be used instead.

r? @Centril

rustc: don't just show raw DefIndex's in BrNamed's fmt::Debug impl.

Context: these `fmt::Debug` impls only get used with `-Z verbose` (which some tests use).

I was going to print the path like in rust-lang#66850 (or rather, use `DefId`'s `fmt::Debug`, which is close but not as nice), but then I realized that most of the `DefId`s were `crate0:DefIndex(0)`, i.e. the crate root.
As the crate root is not a lifetime, they're clearly dummies of some sort, and we don't have to print anything other than the name for them.

This means that out of all the tests, there's only 5 instances of `BrNamed` that now print the full path to the lifetime parameter, and everything else is shorter instead, which doesn't feel too bad.

cc @nikomatsakis

…trochenkov

Add crc and crypto to target feature whitelist on arm

aarch32 (ARMv8 32-bit) supports crc and crypto.

add reusable MachineStop variant to Miri engine error enum

Replace the Miri-tool-specific `Exit` error variant with something dynamically typed that all clients of the Miri engine can use.

r? @oli-obk
Cc rust-lang#66902