Merge #745: Improved PublicKey and XOnlyPublicKey Debug impl

ca32f7b improved PublicKey debug impl (Liam Aharon)

Pull request description:

  Closes #729

  Adjusts `Debug` impls to write serialized hex representation of the keys rather than the inner u8 bytes.

ACKs for top commit:
  apoelstra:
    ACK ca32f7b successfully ran local tests
  tcharding:
    ACK ca32f7b

Tree-SHA512: e73c10733fe3b493492c16f6b2e68149339395b882c70d2d80b9b5e0d75ec671155b09a101ca019e44260413ecb82e93919f2caf0d2508b5baa641e839689909

src/key.rs

@@ -144,7 +144,7 @@ impl str::FromStr for SecretKey {
 /// ```
 /// [`bincode`]: https://docs.rs/bincode
 /// [`cbor`]: https://docs.rs/cbor
-#[derive(Copy, Clone, Debug, PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[derive(Copy, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
 #[repr(transparent)]
 pub struct PublicKey(ffi::PublicKey);
 impl_fast_comparisons!(PublicKey);
@@ -163,6 +163,10 @@ impl fmt::Display for PublicKey {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::LowerHex::fmt(self, f) }
 }
 
+impl fmt::Debug for PublicKey {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::LowerHex::fmt(self, f) }
+}
+
 impl str::FromStr for PublicKey {
     type Err = Error;
     fn from_str(s: &str) -> Result<PublicKey, Error> {
@@ -1138,7 +1142,7 @@ impl CPtr for Keypair {
 /// ```
 /// [`bincode`]: https://docs.rs/bincode
 /// [`cbor`]: https://docs.rs/cbor
-#[derive(Copy, Clone, Debug, PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[derive(Copy, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
 pub struct XOnlyPublicKey(ffi::XOnlyPublicKey);
 impl_fast_comparisons!(XOnlyPublicKey);
 
@@ -1156,6 +1160,10 @@ impl fmt::Display for XOnlyPublicKey {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::LowerHex::fmt(self, f) }
 }
 
+impl fmt::Debug for XOnlyPublicKey {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::LowerHex::fmt(self, f) }
+}
+
 impl str::FromStr for XOnlyPublicKey {
     type Err = Error;
     fn from_str(s: &str) -> Result<XOnlyPublicKey, Error> {