b3188bbac3 Add `Transaction` accessors to `SighashCache` (Martin Habovstiak)
7c6854fe02 Use `Borrow` instead of `Deref` in `SighashCache` (Martin Habovstiak)
Pull request description:
This changes the bound from `Deref<Target = Transaction>` to `Borrow<Transaction>` (with respective `mut` changes) and adds accessors.
Closes#1423 (PSBT stuff will be separate issue).
ACKs for top commit:
tcharding:
ACK b3188bbac3
apoelstra:
ACK b3188bbac3
Tree-SHA512: 9db2c5890b26e9eefd483d697b42e84b1d7d3b8676fc39b4f39075c149e12697aa538828a757f9187578a958d72a592bb913f8f5788c93feb273db5370979d99