We got compile errors like:
/home/build/opm-simulators/opm/simulators/linalg/FlexibleSolver1.cpp:24:1: required from here
/usr/include/dune/istl/ilu.hh:140:29: error: 'double' is not a class, struct, or union type
without this patch.
Hence we use the new internal ILU functions if available.
Previously, the user had to specify it in the json file read from the
FlexibleSolver or 1 was used. Unfortunately, the index depends on the
model used and it seem rather opaque to a user what that index is.
With this commit we determine the pressure index from the model.
