Just to make sure we don't accidentally break this in the future.

Fixes rust-lang#32412

…=alexcrichton

Document heap allocation location guarantee

```
14:25 < aidanhs> is there any guarantee that boxes will not move the value on the heap when they are moved?
14:26 <@steveklabnik> aidanhs: ... i'm not sure if it's a guarantee, but it follows, generally
14:26 <@steveklabnik> aidanhs: moves mean memcpy, so you're memcpying the structure of the box itself, which is copying the pointer
14:26 <@steveklabnik> so the pointer won't be updated
14:26 <@steveklabnik> moves cannot do complex things like move the memory around on the heap
14:26 <@kmc> aidanhs: I would say it's guaranteed
14:27 < aidanhs> steveklabnik: yeah, that's what I was thinking, it'd be pretty strange for rust to do something, but I couldn't find any docs one way or the other
14:27 <@steveklabnik> kmc: aidanhs yeah, it's like a borderline thing that we don't explicitly guanratee but i think IS guaranteed by our other guarantees
14:27 <@steveklabnik> mostly that move == memcpy
14:28 < aidanhs> kmc: steveklabnik great thanks! would a PR to the rust reference along these lines be ok?
14:28 < jmesmon> aidanhs: I believe owning_ref has some discussion of that (stable references)
14:29 <@steveklabnik> aidanhs: i would probably take that, yeah
14:29 < aidanhs> jmesmon: thanks, I'll take a look at that
```
https://botbot.me/mozilla/rust/2016-02-22/?msg=60657619&page=18

r? @steveklabnik

std: Add regression test for rust-lang#32074

Just to make sure we don't accidentally break this in the future.

doc: remove needless bindings

The extra syntax is more noise than help in simple examples like this

…lexcrichton

remove broken config

Fixes rust-lang#32412

…s, r=steveklabnik

Add note on `str` being an unsized type in strings section of book

The book section on Rust strings mentions `&str` and `String` but does not address why `str` is not used directly. This adds a short blurb and a link to the unsized types chapter. The second draft of the book will go more in-depth on this, but this should help a bit for now. Thanks #rust for clarifying this point, and let me know if it needs rewording or different placement 😄.

CC @steveklabnik @Kimundi

Avoid page reload upon hitting "S" when browsing documentation in local mode

The problem seems to have been introduced with commit 2910c00