Fixes rust-lang#19245.

Fixes rust-lang#15755

The collections were promoted to stable by mistake and do not match RFC 509.
This reverts the stability back to unstable.

[breaking-change] since previously stable API became unstable.

Fixes rust-lang#21193

* Use range notation instead of deprecated `range()`

* Remove deprecated `u` integer suffixes used in ranges

* Replace deprecated `i` integer suffixes with `is` for vector numbers

`Thread::spawn()` still gives "use of unstable item" warning which I
hadn't found a way to fix.

The mentioned method are no longer part of Thread. Spawned threads are
detached by default as of now.

Replace deprecated integer suffixes. Remove integer type notations
altogether where possible. Replace uses of deprecated `range()`
function with range notation.

Fixes rust-lang#20071.

I searched for times when we were hiding functions with # in the documentation,
and fixed them to not use it unless neccesary.

I also made random improvements whenever I changed something. For example,
I changed Example to Examples, for consistency.

Fixes rust-lang#13423

Fix all usage of int/uint/i/u in the book.

The example of the `Index` and `IndexMut` trait contained too much `Foo`.
It now contains a bit more `Bar` to make things clearer which parts are
defining the type of the index.

Fixes rust-lang#10489.

Fixes rust-lang#21249
Fixes rust-lang#11540

In accordance with [collections reform part 2][rfc] this macro has been moved to
an external [bitflags crate][crate] which is [available though
crates.io][cratesio]. Inside the standard distribution the macro has been moved
to a crate called `rustc_bitflags` for current users to continue using.

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0509-collections-reform-part-2.md
[crate]: https://github.com/rust-lang/bitflags
[cratesio]: http://crates.io/crates/bitflags

The major user of `bitflags!` in terms of a public-facing possibly-stable API
today is the `FilePermissions` structure inside of `std::io`. This user,
however, will likely no longer use `bitflags!` after I/O reform has landed. To
prevent breaking APIs today, this structure remains as-is.

Current users of the `bitflags!` macro should add this to their `Cargo.toml`:

    bitflags = "0.1"

and this to their crate root:

    #[macro_use] extern crate bitflags;

Due to the removal of a public macro, this is a:

[breaking-change]

"Idiomatic code should not use extra whitespace in the middle of a line to provide alignment."
http://aturon.github.io/style/whitespace.html

I realize the linked page still needs an RFC, but the docs should be written in accordance with the guidelines nevertheless.