rust/library
bors 3bfeffd55b Auto merge of #95904 - paolobarbolini:vecdeque-specextend, r=the8472
Add VecDeque::extend from vec::IntoIter and slice::Iter specializations

Inspired from the [`Vec` `SpecExtend` implementation](027a232755/library/alloc/src/vec/spec_extend.rs), but without the specialization for `TrustedLen` which I'll look into in the future.

Should help #95632 and https://github.com/KillingSpark/zstd-rs/pull/17

## Benchmarks

Before

```
test vec_deque::bench_extend_bytes    ... bench:         862 ns/iter (+/- 10)
test vec_deque::bench_extend_vec      ... bench:         883 ns/iter (+/- 19)
```

After

```
test vec_deque::bench_extend_bytes    ... bench:           8 ns/iter (+/- 0)
test vec_deque::bench_extend_vec      ... bench:          24 ns/iter (+/- 1)

```
2022-04-28 09:27:21 +00:00
..
2022-04-11 21:40:31 -04:00