Use associated_type_bounds where applicable - closes #61738

Tweak mismatched types error

- Change expected/found for type mismatches in `break`
- Be more accurate when talking about diverging match arms
- Tweak wording of function without a return value
- Suggest calling bare functions when their return value can be coerced to the expected type
- Give more parsing errors when encountering `foo(_, _, _)`

Fix #51767, fix #62677, fix #63136, cc #37384, cc #35241, cc #51669.

Give built-in macros stable addresses in the standard library

Continuation of https://github.com/rust-lang/rust/pull/62086.

Derive macros corresponding to traits from libcore are now available through the same paths as those traits:
- `Clone` - `{core,std}::clone::Clone`
- `PartialEq` - `{core,std}::cmp::PartialEq`
- `Eq` - `{core,std}::cmp::Eq`
- `PartialOrd` - `{core,std}::cmp::PartialOrd`
- `Ord` - `{core,std}::cmp::Ord`
- `Default` - `{core,std}::default::Default`
- `Debug` - `{core,std}::fmt::Debug`
- `Hash` - `{core,std}::hash::Hash`
- `Copy` - `{core,std}::marker::Copy`

Fn-like built-in macros are now available through libcore and libstd's root module, by analogy with non-builtin macros defined by libcore and libstd:
```rust
{core,std}::{
    __rust_unstable_column,
    asm,
    assert,
    cfg,
    column,
    compile_error,
    concat,
    concat_idents,
    env,
    file,
    format_args,
    format_args_nl,
    global_asm,
    include,
    include_bytes,
    include_str,
    line,
    log_syntax,
    module_path,
    option_env,
    stringify,
    trace_macros,
}
```

Derive macros without a corresponding trait in libcore or libstd are still available only through prelude (also see https://github.com/rust-lang/rust/pull/62507).
Attribute macros also keep being available only through prelude, mostly because they don't have an existing practice to follow. An advice from the library team on their eventual placement would be appreciated.
```rust
    RustcDecodable,
    RustcEncodable,
    bench,
    global_allocator,
    test,
    test_case,
```

r? @alexcrichton

Stabilize duration_float

Closes: #54361

Update LLVM submodule

Fixes #63361.

r? @alexcrichton

Fix #62677

Rollup of 7 pull requests

Successful merges:

 - #62672 (Deprecate `try!` macro)
 - #62950 (Check rustbook links on all platforms when running locally)
 - #63114 (Remove gensym in format_args)
 - #63397 (Add tests for some ICEs)
 - #63403 (Improve test output)
 - #63404 (enable flt2dec tests in Miri)
 - #63407 (reduce some test sizes in Miri)

Failed merges:

r? @ghost

reduce some test sizes in Miri

enable flt2dec tests in Miri

With ldexp implemented (thanks to @christianpoveda), we can finally enable these tests in Miri. Well, most of them -- some are just too slow.

Improve test output

I'm continuing to improve the test output for liballoc and libcore

Add tests for some ICEs

Closes #43623
Closes #44405

r? @Centril

Remove gensym in format_args

This also fixes some things to allow us to export opaque macros from libcore:

* Don't consider items that are only reachable through opaque macros as public/exported (so they aren't linted as needing docs)
* Mark private items reachable from the root of libcore as unstable - they are now reachable (in principle) in other crates via macros in libcore

r? @petrochenkov

Check rustbook links on all platforms when running locally

cc https://github.com/rust-lang/rust/issues/62739

Deprecate `try!` macro

Replaces #62077

Fixes rust-lang/rust-clippy#1361
Fixes #61000

Update LLVM submodule

This pulls in a newer version of the LLVM 9 release branch.

Fixes #62932.

r? @alexcrichton

Merge recent changes into master