`std::ops::Range` does not implement `std::hash::Hash`

`Range` should implement `Hash` if the value it holds implements `Hash`.

Something like:

```
impl<T> core::hash::Hash for core::ops::Range<T> where T: core::hash::Hash {
    fn hash<H>(&self, state: &mut H) where H: core::hash::Hasher {
        core::hash::Hash::hash(self.start, state);
        core::hash::Hash::hash(self.end, state);
    }
}
```
