Maintain ODEPACK under fortran-lang

[certik]

Similar to FFTPACK (#40) and QUADPACK (#43), we should also maintain ODEPACK under fortran-lang. This has been first mentioned in scipy/scipy#13229, where they have to maintain ODEPACK specific patches inside SciPy.

Instead, we should maintain a new de-facto "upstream" home for ODEPACK, maintaining the code to ensure it compiles with recent Fortran compilers on all architectures. Then SciPy can just copy the sources into their tree. (Down the road, as fpm becomes more widely used, we can discuss other ways of SciPy depending on these packages.)

[dimpase]

I record further progress on modernising ODEPACK on scipy/scipy#13222 (and as far as SciPy is concerned, also ARPACK-NG needs updating).