Merge #462: derive Hash for RecoverableSignature

e275166 derive Hash for RecoverableSignature (NicolaLS)

Pull request description:

  It would be nice to also derive Hash for `RecoverableSignature` so data structures containing it don't have to implement it themself if they need to derive Hash

ACKs for top commit:
  apoelstra:
    ACK e275166

Tree-SHA512: 418337e16e82a5e736c54d123450fdb164f4776db68952cf8095b36c501436446542821d554fa781dffa0f9067fc2464833a6c461897e655ff4449018da12ca2

src/ecdsa/recovery.rs

@@ -28,7 +28,7 @@ use crate::ffi::recovery as ffi;
 pub struct RecoveryId(i32);
 
 /// An ECDSA signature with a recovery ID for pubkey recovery.
-#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
 pub struct RecoverableSignature(ffi::RecoverableSignature);
 
 impl RecoveryId {