So all comes in the order union, intersection, difference and
symmetric_difference.

This adds an `--extern` flag to `rustdoc` much like the compiler's to
specify the path where a given crate can be found.

This adds the alt_std_name field to the Session's Options type.
I'm using this in an external tool to control which libraries
a crate links to.

This provides a way for clients of the rustc library to add
their own features to the pipeline.

Helpful for users of rustc as a library.

It's harder to run rustc correctly without it.

The long hash just takes up space and you can discover the main hash through the
`rustc --version verbose` command.

In f1ad4251, I changed the handling
of macros, to prevent macro invocations from occurring in fully expanded
source. Instead, I added a side table. It contained only the
spans of the macros, because this was the only information required
in order to make macro export work.

However, librustdoc was also affected by this change, since it
extracts macro information in a similar way. As a result of the earlier
change, exported macros were no longer documented.

In order to repair this, I've adjusted the side table to contain whole
items, rather than just the spans.

We now build the game at the end of the first section.

I wanted to do it as we went along, but it's too hard with these fundamentals
not in place. The rest will do the 'as we go' approach, but I think this is
better.

The algorithm was already based on bytes internally.

Also use byte literals instead of casting u8 to char for matching.

[breaking-change] The `InvalidBase64Character` variant of the `FromBase64Error` enum was renamed to `InvalidBase64Byte`, and contains a `u8` instead of a `char`.

r? @alexcrichton

Implements RFC #168.

Closes #8709

Used `HashMap` and `HashSet` as the base of most examples. Could change it up with different containers, but I don't think it's a big deal.

Makes working with syntax deriving a bit more pleasuring. For instance, once can use local (non-static) strings anywhere inside `TraitDef` now.

Fix small typo in guide.

Summary:

* alloc::rc module stable
* Rc type stable
* Functions relating to weak references experimental
* core::cmp module stable
* PartialEq/Eq/PartialOrd/Ord unstable because trait reform will make them change again
* Equiv experimental because there may be better sol'ns
* lexical_ordering deprecated because it can be done trivially with the Ord trait
* min/max stable
* std::task module stable
* TaskBuilder::stdout/stderr experimental because we aren't certain we want to configure the environment this way
* try_future experimental because Future is experimental
* try unstable because the error type might change
* deschedule/failing unstable

The major thing I did differently than previously-discussed is that I made `try` experimental: there's been discussion that the error type `Box<Any + Send>` is not sufficient.


Per https://github.com/rust-lang/meeting-minutes/blob/master/Meeting-API-review-2014-07-16.md.

Implements RFC #168.

Fix for #15780.

`call_visit_glue` is only ever called from trans_intrinsic, and the
block won't be unreachable there. Also, the comment doesn't make sense
anymore. When the code was introduced in 38fee952 the function was
also responsible for the cleanup glue, which is no longer the case.

While we're at it, also fixed the debug message to output the right
function name.

Closes #8709

Simplify example in 5.2 to remove hidden `#[deriving(Show)]`. Traits haven't been introduced yet and now it's easier to just type in the code and expect it to work. Add in some examples for constructing the enum types. Explicitly expose `#![feature(struct_variant)]` in the code to make it more transparent, this bit me when I worked through the tutorial.

Add references in chapter 8 to later chapters describing `Rc`, `Gc` and `Send`. This is a simple fix for #15293.

Simplify vector indexing example in chapter 13 and removed hidden, unnecessary, code. Gave an example usage of the derived `Rand` trait in chapter 17.

Removed references to removed 'extra' crate.

This implements RFC 39. Omitted lifetimes in return values will now be
inferred to more useful defaults, and an error is reported if a lifetime
in a return type is omitted and one of the two lifetime elision rules
does not specify what it should be.

This primarily breaks two uncommon code patterns. The first is this:

    unsafe fn get_foo_out_of_thin_air() -> &Foo {
        ...
    }

This should be changed to:

    unsafe fn get_foo_out_of_thin_air() -> &'static Foo {
        ...
    }

The second pattern that needs to be changed is this:

    enum MaybeBorrowed<'a> {
        Borrowed(&'a str),
        Owned(String),
    }

    fn foo() -> MaybeBorrowed {
        Owned(format!("hello world"))
    }

Change code like this to:

    enum MaybeBorrowed<'a> {
        Borrowed(&'a str),
        Owned(String),
    }

    fn foo() -> MaybeBorrowed<'static> {
        Owned(format!("hello world"))
    }

Closes #15552.

[breaking-change]

r? @nick29581

This branch of try_send() just forgot to wake up any receiver waiting for data.

Closes #15761

This is now linked to in the guide, so I want to make sure it's good. This
adds a bit more explanation, and brings usage in line with current good style.

This is accomplished by rewriting static expressions into equivalent patterns.
This way, patterns referencing static variables can both participate
in exhaustiveness analysis as well as be compiled down into the appropriate
branch of the decision trees that match expressions are codegened to.

Fixes #6533.
Fixes #13626.
Fixes #13731.
Fixes #14576.
Fixes #15393.