a5993426fd bitcoin: Improve rustdocs on extern crates (Tobin C. Harding)
Pull request description:
Make slight improvement to the extern crates we re-export from `bitcoin`.
ACKs for top commit:
apoelstra:
ACK a5993426fddea85c29ac6cd5a0e3096988d72b03; successfully ran local tests
Tree-SHA512: bb857316fc2606aa553f15e1c9fcf8dd87374e170121fe30cf9e44ae190f873f94c113af49b096cb49a65fd68d1bf24732e3f1aba04861e2ae934414f30473c6