13cbead947 Use NumOpResult instead of Option (yancy)
002a0382aa Mark function constant (yancy)
Pull request description:
Prefer the more descriptive NumOpResult return type over Option where return types are fallible.
Closes https://github.com/rust-bitcoin/rust-bitcoin/issues/4419
ACKs for top commit:
apoelstra:
ACK 13cbead94766987f59482b1fbc1d0ebd0799737c; successfully ran local tests
tcharding:
ACK 13cbead947
Kixunil:
ACK 13cbead947
Tree-SHA512: 1a870962dcafe901a07abd93bd8075e41696341c1a4b3efef615493c73d5e5728bbc2326f8c2c95b9034ab001d0b3c668c9d64793ab03486d3a19f31df907c96