improve clone_from_slice performance
add intmax
Add assume intrinsic

Adds an `assume` intrinsic that gets translated to llvm.assume. It is
used on a boolean expression and allows the optimizer to assume that
the expression is true.

This implements #18051.
Improve documentation of assume intrinsic.
Parser: Fix spans of explicit self arg idents
[Docs] intro typo
[Docs] more intro typos
Remove a number of deprecated crates

All of these crates have been deprecated for some time and properly live in the
rust-lang organization as cargo-based crates.

To update your code, depend on the rust-lang/foo repository via cargo.

[breaking-change]
Remove a large amount of deprecated functionality

Spring cleaning is here! In the Fall! This commit removes quite a large amount
of deprecated functionality from the standard libraries. I tried to ensure that
only old deprecated functionality was removed.

This is removing lots and lots of deprecated features, so this is a breaking
change. Please consult the deprecation messages of the deleted code to see how
to migrate code forward if it still needs migration.

[breaking-change]
Guide: Fix test count
Test fixes and rebase conflicts
auto merge of #18070 : alexcrichton/rust/spring-cleaning, r=aturon

This is a large spring-cleaning commit now that the 0.12.0 release has passed removing an amount of deprecated functionality. This removes a number of deprecated crates (all still available as cargo packages in the rust-lang organization) as well as a slew of deprecated functions. All `#[crate_id]` support has also been removed.

I tried to avoid anything that was recently deprecated, but I may have missed something! The major pain points of this commit is the fact that rustc/syntax have `#[allow(deprecated)]`, but I've removed that annotation so moving forward they should be cleaned up as we go.
auto merge of #18186 : cakebaker/rust/fix_test_count, r=alexcrichton
mk/rt: "export CC" does not seem to work (gcc observed), use explicit shell variables instead
Some String Guide improvements.

Fixes #17340
auto merge of #18145 : neilpa/rust/master, r=steveklabnik

Noticed a type while reading through the intro
New Guide: crates and modules
Stability lint checker now handles nested macros.

Closes #17185.
auto merge of #17453 : steveklabnik/rust/gh17340, r=alexcrichton

/cc @huonw
auto merge of #17555 : steveklabnik/rust/module_guide, r=alexcrichton

This is an almost-done draft of a guide on crates and modules. This is a hard guide to get right, I had to remove a chunk of the Guide because it was confusing.

I've also pushed up https://github.com/steveklabnik/phrases which has matching code. Whenever we finish this guide, I think it'd be good to have a sample crate like this in the rust-lang org for people to compare against. The hardest part of a guide like this is that it depends on multiple files being correct, and being able to point to a repository would be very helpful.

Things yet to do:

1. external crates via cargo
2. documentation

I'm super open to still revising this if it's still confusing. There's been a lot of Reddit discussion about the module system, and I tried to incorporate those posts and the comments into this.