this was due to a missing initialization of the MPI. Because
MPI_Finalize should probably called even if the program is aborted due
to an exception, this is done using a helper class. (which does the
same job as Dune::MPIHelper, but is much simpler.)
basically the only Dune thing which is still used are the FieldVector
and FieldMatrix classes used by some constraint solvers. Until
something similar goes into opm-core, opm-material must depend on
dune-common...