Remove macro_use from stable_hasher.

Normal `use` items are nicer.

compiler/rustc_data_structures/src/fingerprint.rs

@@ -1,3 +1,4 @@
+use crate::stable_hasher::impl_stable_traits_for_trivial_type;
 use crate::stable_hasher::{Hash64, StableHasher, StableHasherResult};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use std::hash::{Hash, Hasher};