DSTify Hash

- The signature of the `*_equiv` methods of `HashMap` and similar structures
have changed, and now require one less level of indirection. Change your code
from:

```
hashmap.find_equiv(&"Hello");
hashmap.find_equiv(&&[0u8, 1, 2]);
```

to:

```
hashmap.find_equiv("Hello");
hashmap.find_equiv(&[0u8, 1, 2]);
```

- The generic parameter `T` of the `Hasher::hash<T>` method have become
`Sized?`. Downstream code must add `Sized?` to that method in their
implementations. For example:

```
impl Hasher<FnvState> for FnvHasher {
    fn hash<T: Hash<FnvState>>(&self, t: &T) -> u64 { /* .. */ }
}
```

must be changed to:

```
impl Hasher<FnvState> for FnvHasher {
    fn hash<Sized? T: Hash<FnvState>>(&self, t: &T) -> u64 { /* .. */ }
    //      ^^^^^^
}
```

[breaking-change]

src/librustdoc/html/render.rs

@@ -2123,7 +2123,7 @@ impl<'a> fmt::Show for Sidebar<'a> {
 
         fn block(w: &mut fmt::Formatter, short: &str, longty: &str,
                  cur: &clean::Item, cx: &Context) -> fmt::Result {
-            let items = match cx.sidebar.find_equiv(&short) {
+            let items = match cx.sidebar.find_equiv(short) {
                 Some(items) => items.as_slice(),
                 None => return Ok(())
             };