This contains significant rebase / merge / testing work by Naut
<lbrynaut@protonmail.com>, Anthony Fieroni <bvbfan@abv.bg> and Brannon
King <countprimes@gmail.com>.
This change marks the already-existing bitcoin-wallet.1 manpage file for
installation together with the others. Previously, only bitcoind.1,
bitcoin-cli.1, bitcoin-tx.1 and bitcoin-qt.1 would be installed.