std: Stabilize the `hash` module

This commit is an implementation of [RFC 823][rfc] which is another pass over
the `std::hash` module for stabilization. The contents of the module were not
entirely marked stable, but some portions which remained quite similar to the
previous incarnation are now marked `#[stable]`. Specifically:

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0823-hash-simplification.md

* `std::hash` is now stable (the name)
* `Hash` is now stable
* `Hash::hash` is now stable
* `Hasher` is now stable
* `SipHasher` is now stable
* `SipHasher::new` and `new_with_keys` are now stable
* `Hasher for SipHasher` is now stable
* Many `Hash` implementations are now stable

All other portions of the `hash` module remain `#[unstable]` as they are less
commonly used and were recently redesigned.

This commit is a breaking change due to the modifications to the `std::hash` API
and more details can be found on the [RFC][rfc].

Closes #22467
[breaking-change]

1 files changed, 1 insertions, 2 deletions

diff --git a/src/test/bench/core-set.rs b/src/test/bench/core-set.rs
index 1d440c4540c..7cbc4e1d7af 100644
--- a/src/test/bench/core-set.rs
+++ b/src/test/bench/core-set.rs
@@ -18,7 +18,6 @@ extern crate rand;
 use std::collections::BTreeSet;
 use std::collections::BitvSet;
 use std::collections::HashSet;
-use std::collections::hash_map::Hasher;
 use std::hash::Hash;
 use std::env;
 use std::time::Duration;
@@ -43,7 +42,7 @@ trait MutableSet<T> {
     fn contains(&self, k: &T) -> bool;
 }
 
-impl<T: Hash<Hasher> + Eq> MutableSet<T> for HashSet<T> {
+impl<T: Hash + Eq> MutableSet<T> for HashSet<T> {
     fn insert(&mut self, k: T) { self.insert(k); }
     fn remove(&mut self, k: &T) -> bool { self.remove(k) }
     fn contains(&self, k: &T) -> bool { self.contains(k) }