Update required: Fortran interface for accessing new CDF-5 types

PR #525 has introduced support for new CDF-5 external data types
in SCORPIO. Presently, only the C interface has been updated to
utilize these new data types. It is essential to extend this support
to include the corresponding Fortran types (NF_*).

Additionally, the unit testing framework needs to be expanded to
cover a broader range of data types.