libnova: 0.15.0 Initial commit of formula

libnova is a general purpose, double precision, Celestial Mechanics, Astrometry
and Astrodynamics library. The intended audience of libnova is C / C++
programmers, astronomers and anyone else interested in calculating positions of
astronomical objects or celestial mechanics

It is a dependency for the INDI Library, used for the automation and control
of astronomical instruments, which will also be submitted