b8067da934 Parse MSRV minor version number from env (yancy)
Pull request description:
Parse MSRV minor version number from env
replaces: https://github.com/rust-bitcoin/rust-bitcoin/pull/3145
ACKs for top commit:
Kixunil:
ACK b8067da934
tcharding:
ACK b8067da934
apoelstra:
ACK b8067da934 successfully ran local tests
Tree-SHA512: 60b3898c9b2739ca4858218b21d5c136b91b6ef45b1dc8f798d97aac861c42d046f114efcefdfa79f514d6da392f715a715ee6b3f230eb459f34e554b48ccf0e