flow_ebos*: make it build and (the sequential part) work if dune-fem is available

in particular, this implied some changes to the MPI initialization
code. since dune-fem's GridPart class currently has issues with
CpGrid's implementation of loadBalance(), parallel computations still
do not work if dune-fem is around, but at least sequential ones now
do even if MPI is enabled.

examples/flow_ebos_polymer.cpp

@@ -22,12 +22,17 @@
 #include "config.h"
 #endif // HAVE_CONFIG_H
 
-#include <opm/material/densead/Evaluation.hpp>
-#include <opm/autodiff/DuneMatrix.hpp>
+#include <opm/common/ResetLocale.hpp>
 #include <dune/grid/CpGrid.hpp>
 #include <opm/autodiff/SimulatorFullyImplicitBlackoilEbos.hpp>
 #include <opm/autodiff/FlowMainEbos.hpp>
 
+#if HAVE_DUNE_FEM
+#include <dune/fem/misc/mpimanager.hh>
+#else
+#include <dune/common/parallel/mpihelper.hh>
+#endif
+
 namespace Ewoms {
 namespace Properties {
 NEW_TYPE_TAG(EclFlowPolymerProblem, INHERITS_FROM(EclFlowProblem));
@@ -37,6 +42,18 @@ SET_BOOL_PROP(EclFlowPolymerProblem, EnablePolymer, true);
 // ----------------- Main program -----------------
 int main(int argc, char** argv)
 {
+    // we always want to use the default locale, and thus spare us the trouble
+    // with incorrect locale settings.
+    Opm::resetLocale();
+
+    // initialize MPI, finalize is done automatically on exit
+#if HAVE_DUNE_FEM
+    Dune::Fem::MPIManager::initialize(argc, argv);
+    const int myRank = Dune::Fem::MPIManager::rank();
+#else
+    const int myRank = Dune::MPIHelper::instance(argc, argv).rank();
+#endif
+
     Opm::FlowMainEbos<TTAG(EclFlowPolymerProblem)> mainfunc;
     return mainfunc.execute(argc, argv);
 }