bindings: Convert Fortran MPI- and non-MPI implementations to submodules
Created by: bradking
Convert the separate modules implementing Fortran adios2_init
and adios2_open
generic procedure signatures for MPI and non-MPI variants into submodules. This allows the primary modules to be built first and the implementation submodules built later in separate libraries.
In order to support compilers that do not support Fortran submodules, use preprocessor conditions to optionally build without submodules as before.