astro/libnova: Set maintainer, improve and update 0.15.0

ChangeLog: https://sourceforge.net/p/libnova/libnova/ci/v0.16/tree/ChangeLog

Reporter becomes maintainer. Already maintainer of several ports.

PR: 286058
Reported by: [email protected]