Small fixes for tutorial.

5.2 Simplify example to remove hidden #[deriving(Show)].
    Add example for constructing the enums.

8   Reference later sections describing rc, gc and send.
    Fix for #15293.

13  Simplify BananaMania example to remove hidden code.

17  Gave an example using the derived Rand trait.

Removed references to removed 'extra' crate.
sync: Ensure try_send() wakes up receivers

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

Closes #15761
Remove outdated unreachable check from `call_visit_glue`

`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 38fee9526a 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.
Correct plural of arguments in format_args!
Special case for 0 arguments given in format!
Remove the unneeded final parameter from call_visit_glue

call_visit_glue() is only ever called with None as its last argument, so
we can remove it as well.
Add support for patterns referencing non-trivial statics

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.
Improve documentation for rand::random

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.
librustc: Implement lifetime elision.

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]
auto merge of #15650 : jakub-/rust/patterns-statics, r=pcwalton

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.
auto merge of #15746 : steveklabnik/rust/docs_random, r=alexcrichton

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.
auto merge of #15764 : alexcrichton/rust/issue-15761, r=kballard

This branch of try_send() just forgot to wake up any receiver waiting for data.

Closes #15761
auto merge of #15767 : pcwalton/rust/lifetime-elision, r=nick29581

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
Register new snapshots
auto merge of #15776 : alexcrichton/rust/snapshots, r=huonw
auto merge of #15745 : treeman/rust/tutorial-fixup, r=steveklabnik

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.
auto merge of #15784 : dotdash/rust/unreach, r=luqmana

`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 38fee9526a 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.
auto merge of #15785 : treeman/rust/fix-15780, r=alexcrichton

Fix for #15780.
Allow macros in type expressions