Merge rust-bitcoin/rust-bitcoin#951: Add PSBT alias

f92854a Add PSBT alias (Tobin Harding)

Pull request description:

  Programmers are inherently lazy and for good reason. I'm yet to see
  anyone write `PartiallySignedTransaction` in code that uses
  `rust-bitcoin`, its too obvious to add a type alias for PSBTs, let's
  just do it ourselves to save everyone else having to do so.

  Add public type alias `Psbt` for `PartiallySignedTransaction`.

ACKs for top commit:
  apoelstra:
    ACK f92854a
  sanket1729:
    ACK f92854a

Tree-SHA512: 1f56ac236d34a89bbb557ada147f05d8a8ce961dad3ad921f10f26c597b91ecc8e15070f8825774745e5333ba5282962830a3cc0c53b93f147be93ab566b1b9e

src/util/psbt/mod.rs

@@ -46,6 +46,9 @@ use self::map::Map;
 
 use util::bip32::{ExtendedPubKey, KeySource};
 
+/// Partially signed transaction, commonly referred to as a PSBT.
+pub type Psbt = PartiallySignedTransaction;
+
 /// A Partially Signed Transaction.
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]