Merge branch 'v2.4' into v2.5

CHANGES/v2.4.md

patches/gromacs-2018.6.config

patches/gromacs-2018.6.diff/src/gromacs/CMakeLists.txt

.../gromacs-2018.6.diff/src/gromacs/CMakeLists.txt.preplumed

patches/gromacs-2018.6.diff/src/gromacs/mdlib/force.cpp

...gromacs-2018.6.diff/src/gromacs/mdlib/force.cpp.preplumed

patches/gromacs-2018.6.diff/src/gromacs/mdlib/minimize.cpp

...macs-2018.6.diff/src/gromacs/mdlib/minimize.cpp.preplumed

patches/gromacs-2018.6.diff/src/programs/mdrun/md.cpp

...s/gromacs-2018.6.diff/src/programs/mdrun/md.cpp.preplumed

patches/gromacs-2018.6.diff/src/programs/mdrun/mdrun.cpp

...romacs-2018.6.diff/src/programs/mdrun/mdrun.cpp.preplumed

patches/gromacs-2018.6.diff/src/programs/mdrun/repl_ex.cpp

...macs-2018.6.diff/src/programs/mdrun/repl_ex.cpp.preplumed

patches/gromacs-2018.6.diff/src/programs/mdrun/repl_ex.h

...romacs-2018.6.diff/src/programs/mdrun/repl_ex.h.preplumed

patches/gromacs-2018.6.diff/src/programs/mdrun/runner.cpp

...omacs-2018.6.diff/src/programs/mdrun/runner.cpp.preplumed

patches/gromacs-2018.6.diff/src/programs/mdrun/runner.h

...gromacs-2018.6.diff/src/programs/mdrun/runner.h.preplumed