Emitting or deriving trait implementations

Let's implement all the traits!!

All of the "Derive Blah when possible" issues have code in tree already that they can crib from, so shouldn't be too difficult to write.

Once we start deriving lots of different traits, I expect we may find that we can unify their implementations, or at least make a generic CanDeriveTrait<T: DerivableTrait> kind of generic thing.

• "manually" implement Debug when we cannot derive it: https://github.com/rust-lang-nursery/rust-bindgen/issues/875

• Derive Hash when possible: https://github.com/rust-lang-nursery/rust-bindgen/issues/876

  • "manually" implement Hash when we cannot derive it: https://github.com/rust-lang-nursery/rust-bindgen/issues/877

• Derive PartialEq when possible: https://github.com/rust-lang-nursery/rust-bindgen/issues/878

  • "manually" implement PartialEq when we cannot derive it: https://github.com/rust-lang-nursery/rust-bindgen/issues/879

  • Derive Eq when possible: https://github.com/rust-lang-nursery/rust-bindgen/issues/880

    • "manually" implement Eq when we cannot derive it: https://github.com/rust-lang-nursery/rust-bindgen/issues/881

• Derive PartialOrd when possible: https://github.com/rust-lang-nursery/rust-bindgen/issues/882

  • "manually" implement PartialOrd when we cannot derive it: https://github.com/rust-lang-nursery/rust-bindgen/issues/883

  • Derive Ord when possible: https://github.com/rust-lang-nursery/rust-bindgen/issues/884

    • "manually" implement Ord when we cannot derive it: https://github.com/rust-lang-nursery/rust-bindgen/issues/885

Start by reviewing the linked issues 875 through 885 and their existing implementations to identify which trait tasks remain unchecked. Determine whether the remaining manual and derived implementations share a workable approach; done means the applicable checklist items are implemented and validated by the corresponding issue tests.