[breaking-change]

This will break any uses of macros that assumed () being a valid literal.

Struct variant field visibility is now inherited. Remove `pub` keywords
from declarations.

Closes #18641

[breaking-change]

This also impls `FormatWriter` for `Vec<u8>`

For consistancy with ToString

This test was somewhat sketchy already with a `loop` around `write`, so this
just adds some explicit synchronization to only call `write` once and guarantee
that the error happens.

Closes #18900

This commit slightly tweaks the counting of impl blocks and structs for
the stability summary (so that the block itself isn't counted for
inherent impls, and the fields aren't counted for structs).

A recent change turned off inheritance for the #[stable] by default, but
failed to catch all the cases where this was being used in std. This
patch fixes that problem.

Hide the search form and expand/collapse buttons, since they aren't useful when printed.

It is necessary to have #[deriving(Default)] for struct containing
cells like Cell<u32>.

The examples in the documentation for syntax::ext::deriving::encodable
are outdated, and do not work. To fix this, the following changes are
applied:

- emit_field() -> emit_struct_field()
- read_field() -> read_struct_field()
- Use Result to report errors
- Add the mut keyword to Encoder/Decoder
- Prefer Encodable::encode() to emit_uint

Use is_some() in clear to simplify the clear loop.

-Adds unit tests for fn get() and fn get_mut() which are currently untested
-Adds unit tests to verify growth of the ringbuffer when reserve is called.
-Adds unit tests to confirm that dropping of items is correct
Move ringbuf to use a raw buffer instead of Option<T>

The previous implementation was very likely to cause panics during
unwinding through this process:

- child panics, drops its receiver
- taskpool comes back around and sends another job over to that child
- the child receiver has hung up, so the taskpool panics on send
- during unwinding, the taskpool attempts to send a quit message to
  the child, causing a panic during unwinding
- panic during unwinding causes a process abort

This meant that TaskPool upgraded any child panic to a full process
abort. This came up in Iron when it caused crashes in long-running
servers.

This implementation uses a single channel to communicate between
spawned tasks and the TaskPool, which significantly reduces the complexity
of the implementation and cuts down on allocation. The TaskPool uses
the channel as a single-producer-multiple-consumer queue.

Additionally, through the use of send_opt and recv_opt instead of
send and recv, this TaskPool is robust on the face of child panics,
both before, during, and after the TaskPool itself is dropped.

Due to the TaskPool no longer using an `init_fn_factory`, this is a

[breaking-change]

otherwise, the API has not changed.

If you used `init_fn_factory` in your code, and this change breaks for
you, you can instead use an `AtomicUint` counter and a channel to
move information into child tasks.

[breaking-change]
Any uses of Buffer::lines() and Buffer::chars() will need to use the new trait std::io::BufferPrelude.