Merge three rules into one following @cramertj

remove italic as per @GuillaumeGomez suggestion

Make UnsafeCell doc easier to follow

Optimized error reporting for recursive requirements #47720

Fixes #47720

Add `-Zteach` documentation

Add extra inline documentation to E0019, E0016, E0013, E0396, E0017,
E0018, E0010, E0022, E0030, E0029, E0033, E0026 and E0027.

Follow up to #47652.

Compiletest: delete the compiled program once its test is done.

Reduces CI disk usage which prevents #48118 from succeeding.

This isn't a perfect heuristic, but since the amount of run-fail tests
is far lower than run-pass tests for now, it should be sufficient to
ensure that we don't run into CI limits. This makes it possible to run
the test binary manually (e.g., under gdb/lldb) if it failed to attempt
to find out why.

This should save a lot of space on musl test cases (whose standard library
are linked statically).

Implement `?` macro repetition

See rust-lang/rfcs#2298 (with disposition merge)

Fix oversized loads on x86_64 SysV FFI calls

The x86_64 SysV ABI should use exact sizes for small structs passed in
registers, i.e. a struct that occupies 3 bytes should use an i24,
instead of the i32 it currently uses.

Refs #45543

Emit data::Impl in save-analysis

As discussed on [internals.rust-lang](https://internals.rust-lang.org/t/rustdoc2-rls-analysis-and-the-compiler-help-wanted/6592/5), this PR emits `rls-data::Impl` in the save-analysis.

A number of questions are outstanding:

- [x] A few `???` around row 356. We need to discuss what goes here, if anything.
- [ ] ~~Deriving `id` for impl using hashing. Is this going to clash with rustc defids?~~
- [ ] ~~Deriving `id` for impl using hashing. Is the conversion from 64 bit -> 32 bit problematic?~~
- [x] Need a new rls-data with an `id` field in `Impl` struct.
- [ ] ~~Need a new rls-data which `derive` `Hash` for `ImplKind` enum.~~

 rustc_mir: insert a dummy access to places being matched on, when building MIR.

Fixes #47412 by adding a `_dummy = Discriminant(place)` before each `match place {...}`.

r? @nikomatsakis

Update RELEASES.md for 1.24.0

[rendered](https://github.com/Aaronepower/rust/blob/master/RELEASES.md)

Rollup of 20 pull requests

- Successful merges: #47790, #47835, #47854, #48015, #48047, #48051, #48058, #48059, #48064, #48078, #48080, #48086, #48098, #48101, #48107, #48100, #48085, #48120, #48124, #47547
- Failed merges:

Document the behaviour of infinite iterators on potentially-computable methods

It’s not entirely clear from the current documentation what behaviour
calling a method such as `min` on an infinite iterator like `RangeFrom`
is. One might expect this to terminate, but in fact, for infinite
iterators, `min` is always nonterminating (at least in the standard
library). This adds a quick note about this behaviour for clarification.

Explain unusual debugging code in librustc

Introduced in #47828 to help track down some bugs, it landed a bit hastily so
this is intended on cleaning it up a bit.

fix typos in src/{bootstrap,ci,etc,lib{backtrace,core,fmt_macros}}

via codespell

Update the dlmalloc submodule

A bug was recently fixed in dlmalloc which meant that released memory to the
system accidentally wasn't getting reused, causing programs to be far slower
than they should be!

Introduced in #47828 to help track down some bugs, it landed a bit hastily so
this is intended on cleaning it up a bit.

A bug was recently fixed in dlmalloc which meant that released memory to the
system accidentally wasn't getting reused, causing programs to be far slower
than they should be!

Add fetch_nand to atomics

I think this is all fine but I have little familiarity with the atomic code (or libcore in general) so I may have accidentally done something wrong here...

cc #13226 (the tracking issue)

fix typo: substract -> subtract

Update books for next release

r? @steveklabnik

ci: Actually bootstrap on i686 dist

Right now the `--build` option was accidentally omitted, so we're bootstraping
from `x86_64` to `i686`. In addition to being slower (more compiles) that's not
actually bootstrapping!

Fix visitation order of calls so that it matches execution order. Fixes #48048

r? @nikomatsakis

Hide theme button under menu in mobile mode and fix top margin issue …

Fixes #48060.

r? @QuietMisdreavus

Disallow function pointers to #[rustc_args_required_const]

This commit disallows acquiring a function pointer to functions tagged as
`#[rustc_args_required_const]`. This is intended to be used as future-proofing
for the stdsimd crate to avoid taking a function pointer to any intrinsic which
has a hard requirement that one of the arguments is a constant value.

Note that the first commit here isn't related specifically to this feature, but was necessary to get this working in stdsimd!

intra-doc-links: bail early for linky things

r? @QuietMisdreavus

rustbuild: Pass `ccache` to build scripts

Right now the ccache setting is only used for LLVM, but this tweaks it to also
be used for build scripts so C++ builds like `librustc_llvm` can be a bit
speedier.

Update binaryen to fix -Werror with GCC 8

r? @alexcrichton

rustdoc: Hide `-> ()` in cross crate inlined Fn* bounds

Fix ICE for mismatched args on target without span

Commit 7ed00caa improved our error reporting by including the target function in our error messages when there is an argument count mismatch. A simple example from the UI tests is:

```
error[E0593]: function is expected to take a single 2-tuple as argument, but it takes 0 arguments
  --> $DIR/closure-arg-count.rs:32:53
   |
32 |     let _it = vec![1, 2, 3].into_iter().enumerate().map(foo);
   |                                                     ^^^ expected function that takes a single 2-tuple as argument
...
44 | fn foo() {}
   | -------- takes 0 arguments
```

However, this assumed the target span was always available. This does not hold true if the target function is in `std` or another crate. A simple example from #48046 is assigning `str::split` to a function type with a different number of arguments.

Fix by omitting all of the labels and suggestions related to the target span when it's not found.

Fixes #48046

r? @estebank

Customizable extended tools

This PR adds `build.tools` option to manage installation of extended rust tools.

By default it doesn't change installation. All tools are built and `rls` and `rustfmt` allowed to fail installation.

If some set of tools chosen only those tools are built and installed without any fails allowed.

It solves some slotting issues with extended build enabled: https://bugs.gentoo.org/show_bug.cgi?id=645498

Create a directory for --out-dir if it does not already exist

Currently if `--out-dir` is set to a non-existent directory, the compiler will throw unfriendly messages like `error: could not write output to subdir/example.crate.allocator.rcgu.o: No such file or
directory`, which, while not completely unreadable, isn’t very user-friendly either. This change creates the directory automatically if it does not yet exist.

Remove unused data structures

Cleanup; as far as I can tell the compiler no longer uses these.

derive PartialEq and Eq for `ParseCharError`

unlike the other Parse*Error types, ParseCharError didn't have these implemented for whatever reason