Add a variant of home_for_io that consumes the handle. Refactor out common parts of the home_for_io variants.
Split out starting a listener from accepting incoming connections.

The Listener trait takes two type parameters, the type of connection and the type of Acceptor,
and specifies only one method, listen, which consumes the listener and produces an Acceptor.

The Acceptor trait takes one type parameter, the type of connection, and defines two methods.
The accept() method waits for an incoming connection attempt and returns the result.
The incoming() method creates an iterator over incoming connections and is a default method.

Example:

let listener = TcpListener.bind(addr); // Bind to a socket
let acceptor = listener.listen(); // Start the listener
for stream in acceptor.incoming() {
    // Process incoming connections forever (or until you break out of the loop)
}
Implement BufReader
Don't have format! move out of local variables
Implement support for indicating the stability of items.

There are 6 new compiler recognised attributes: deprecated, experimental,
unstable, stable, frozen, locked (these levels are taken directly from
Node's "stability index"[1]). These indicate the stability of the
item to which they are attached; e.g. `#[deprecated] fn foo() { .. }`
says that `foo` is deprecated.

This comes with 3 lints for the first 3 levels (with matching names) that
will detect the use of items marked with them (the `unstable` lint
includes items with no stability attribute). The attributes can be given
a short text note that will be displayed by the lint. An example:

    #[warn(unstable)]; // `allow` by default

    #[deprecated="use `bar`"]
    fn foo() { }

    #[stable]
    fn bar() { }

    fn baz() { }

    fn main() {
        foo(); // "warning: use of deprecated item: use `bar`"

        bar(); // all fine

        baz(); // "warning: use of unmarked item"
    }

The lints currently only check the "edges" of the AST: i.e. functions,
methods[2], structs and enum variants. Any stability attributes on modules,
enums, traits and impls are not checked.

[1]: http://nodejs.org/api/documentation.html
[2]: the method check is currently incorrect and doesn't work.
auto merge of #8945 : alexcrichton/rust/ifmt-dont-move, r=thestinger
auto merge of #8934 : sfackler/rust/bufreader, r=brson
auto merge of #8921 : huonw/rust/stability, r=brson

Significant progress on #6875, enough that I'll open new bugs and turn that into a metabug when this lands.

Description & example in the commit message.
auto merge of #8954 : anasazi/rust/tcp-acceptor, r=catamorphism

The Listener trait takes two type parameters, the type of connection and the type of Acceptor,
and specifies only one method, listen, which consumes the listener and produces an Acceptor.

The Acceptor trait takes one type parameter, the type of connection, and defines two methods.
The accept() method waits for an incoming connection attempt and returns the result.
The incoming() method creates an iterator over incoming connections and is a default method.

Example:

```rust
let listener = TcpListener.bind(addr); // Bind to a socket
let acceptor = listener.listen(); // Start the listener
for stream in acceptor.incoming() {
    // Process incoming connections forever (a failure will kill the task).
}
```

Closes #8689