This system tests the nonbonded NxN kernel with Lorentz-Berthelot combination
rules (only relevant for x86 SIMD kernels), virtual sites and pressure
coupling. This means the vsite OpenMP code is also tested.

Forces and velocities are not compared because they are not reprodicible within
tolerance. At one time, this test did not work with MPI parallelization. That
might have been because the box size was very tight wrt cutoff. This has now
been relaxed. Further, verlet-buffer-list is now -1 to hard-code rlist, so that
the automatic increase of rlist with GPUs does not make the DD impossible.
