Fixes rust-lang#29234

Fixes rust-lang#29234

Since commit 46068c9, call to `reserve()` on empty vec allocates
exactly requested capacity, so unroll of first iteration may help only
with branch prediction.

* wrap to 80 cols
* small grammar fix, missing 'the'

r? @steveklabnik

…labnik

Did this alphabetically, so I didn't see [how `std` was doing things](https://dxr.mozilla.org/rust/source/src/libstd/lib.rs#215) till I was nearly finished. If you prefer to add crate-level-whitelists like std instead of test-level, I can rebase with that strategy.

A number of these commits can probably be dropped as the crates don't have much to test, and are deprecated. Let me know which if any to drop! (can also squash after review if desired)

r? @steveklabnik

…akis

Since commit 46068c9, call to `reserve()` on empty vec allocates
exactly requested capacity, so unroll of first iteration may help only
with branch prediction.

r? @steveklabnik

r? @steveklabnik

See rust-lang#27305

r? @steveklabnik

This completely abdicates any responsibility to explain what Rust is, instead linking to the website.

My main motivation is that I am still not happy with it, and every time I try to fix it I just write a slightly longer sales pitch than what's on the website.

One thing this paragraph could do is direct people to more information about what is in the repo, or more technical information about the implementation.

* wrap to 80 cols
* small grammar fix, missing 'the'