Compilers and MPI Port Groups

[Sean Farley]

Hello all and Happy Boxing Day!

I have done a complete rewrite of the compilers and mpi port groups
based on suggestions from previous emails. I will try to keep this email
short and provide links for those that want to know more.

Highlights:

- specify which compilers to set via compilers.choose,
  e.g. 'compilers.choose f77 f90 fc'

- functions for testing if fortran has been selected for optional
  interfaces

- portfile author can specify if fortran (or mpi) is required

- unified and have made non-conflicting openmpi and mpich ports; also
  added an openmpi-devel port [1]

- can now select either mpi port as the default mpi installation

Example of a portfile using the new compilers portgroup:
https://smf.io/macports/changeset/compilers

Example of a portfile that uses the mpi portgroup:
https://smf.io/macports/files/mpi/dports/science/hdf5-18/Portfile

The changes I made to the sparskit and hdf5-18 portfiles are just
examples I did for illustrative purposes. I won't push them unless the
portfile author wants it. The mpich and openmpi portfiles need these
changes so that the mpi portgroup will work.

Anyway, I'd like to push this soon so that I can continue other work
(and close a lot of tickets), so it'd be great if others could take a
look at the proposed changes.

[1] https://smf.io/macports/changeset/81bb51 or look at the changelog
https://smf.io/macports/changelog to see all the diffs