* This way the MPI parts of CDI can be compiled without introducing
  an artificial MPI dependency for non-MPI parts.

* This test currently only checks if a single missing value is
  successfully written out and counted on input.

* Add proper formatting of example program output.
* Add test to ensure the examples are working.
* Add better handling of Pointer arguments.
* Add better handling of C char * return values.
* Add helper function for C character length.
* Test that the compiler properly support Fortran/C interop at configure
  time.

* This way it could be used in out-of-source builds with some modifications.

* It's at the moment identical to the 1D test. That will change with the next commit.

* This also adds separate documentation, header, Fortran wrappers and
  pkg-config file for the cdi-pio part of the library

* This will allow for later additions of more complex tests.

* The added pkg.m4 accounts for pkg.m4 sometimes not being available or
  having another version.

* Said generic can be replaced with an MPI-specific version, thus
  cleanly separating serialization of meta-data itself and MPI-
  communication.

* It became obsolete with the improvements to make_fint in r1955.