calc_pressure_gromacs: make it work with gromacs-devel
calc_pressure_gromacs: make it work with gromacs-devel

MrTheodor/csg,MrTheodor/csg,junghans/csg,votca/csg,MrTheodor/csg,MrTheodor/csg,votca/csg,junghans/csg,junghans/csg,votca/csg,junghans/csg,junghans/csg,votca/csg,junghans/csg,MrTheodor/csg