* It wasn't clear whether `?Sized` meant "not `Sized`" or "`Sized` or not `Sized`". According to #rust IRC, it does indeed mean "`Sized` or not `Sized`".
* Use the same language as [Trait std::marker::Sized](https://doc.rust-lang.org/std/marker/trait.Sized.html) about how `Sized` is implicitly bound.

The tracking issue for once_poison was noted as rust-lang#31688 which was closed, so it now points to the new rust-lang#33577.

* Use "special bound syntax" instead of "special syntax". `?Sized` is technically a "bound", but `?Sized` is specialized syntax that _only_ works with `Sized`, and no other Trait.
* Replace "constant size" with "sized".

update tracking issue for once_poison

The tracking issue for once_poison was noted as rust-lang#31688 which was closed, so it now points to the new rust-lang#33577.

… r=alexcrichton

rustdoc: Add doc snippets for trait impls, with a read more link

The read more link only appears if the documentation is more than one line long.

![screenshot from 2016-05-17 06 54 14](https://cloud.githubusercontent.com/assets/1617736/15308544/4c2ba0ce-1bfc-11e6-9add-29de8dc7ac6e.png)

It currently does not appear on non-defaulted methods, since you can document them directly. I could make it so that default documentation gets forwarded if regular docs don't exist.

Fixes rust-lang#33672

r? @alexcrichton

cc @steveklabnik

…r=steveklabnik

Book: small improvement to a table to make it clearer

This table is used as an example of four heap values where two of them got deallocated leaving a gap.
It also has stack variables.
Instead of four stack variables I propose three, that way there's no misleading connection between the number of stack variables and heap variables.
But more importantly: three of the four stack variables had the same name (**y**) which could be confusing to a beginner, I changed this as well.

…abnik

Clarify docs for sort(&mut self)

I documented the memory usage like noted in this issue:
  * Document memory usage of sort() family of functions rust-lang#33419

Clarify the English translation of `?Sized`

* It wasn't clear whether `?Sized` meant "not `Sized`" or "`Sized` or not `Sized`". According to #rust IRC, it does indeed mean "`Sized` or not `Sized`".
* Use the same language as [Trait std::marker::Sized](https://doc.rust-lang.org/std/marker/trait.Sized.html) about how `Sized` is implicitly bound.
* Refer to the syntax as `?Sized`, since it's currently the only allowed trait that can follow `?`.

book: ownership: fix typo

The sentence ends there, so a comma is required.

See:
http://english.stackexchange.com/questions/1469/when-ending-a-list-with-etc-should-there-be-a-comma-before-etc

Update simd syntax

r? @steveklabnik