This will become almacalc 11.0.0. Use f2py to generate a portable
Fortran extension which takes care of type checks and conversions
(unlike ctypes). We are using f2py's "smart way" to wrap the main
almacalc function, by generating a signature file (calc11.pyf) and
tweaking it to suit our interface.

Attempt a minimal packaging setup with careful attention to setup.py
and the rest of the packaging infrastructure (no cargo!).

Write a NumPy-based wrapper for the main almacalc function that takes
care of optional and unused arguments and also finds the builtin JPL
ephemeris file that is installed as package data (if none is provided).
The ephemeris is minimally checked to avoid a nasty Fortran crash.

Add a basic test that can be run via pytest. Generate the expected
output using a Makefile that builds a Fortran test program.

The license is still up for discussion. CALC has been around since at
least 1977 and is considered to be in the public domain by David Gordon,
who has also been the main author of changes since 1988, when it became
necessary to obtain permission from copyright holders to release
software into the public domain. Mark Ashdown and Ludwig Schwardt's code
falls under 3-clause BSD, while the ALMA repository is mostly LGPL.
Another license contender is Zero-Clause BSD, which is effectively
public domain.

Surprisingly, this all works in Python 2.7 with hardly any deviation
from Python 3 idioms, so we might as well support it (for now).