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Remove outdated unreachable check from `call_visit_glue`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.
core: Stabliize core::cmp

Mark Eq, PartialEq, Ord, PartialOrd as unstable: they will change
slightly after trait reform. Equiv as experimental: better solutions
are desired. min/max stable.
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.
std: Stabilize default

All stable.
alloc: Stabilize rc module.

Weak pointers experimental. Most everything else stable.
std: Stabilize task module.

Most stable. deschedule/failing experimental because of concerns about
naming and desirability.

Adds task::name() to replace deprecated task::with_name().
Fix typo.
Document some trait methods.
Implement FromBase64 for &[u8].

The algorithm was already based on bytes internally.

Also use byte literals instead of casting u8 to char for matching.
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]
Fixed lifetimes on syntax deriving structs, implemented Clone
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
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