Merge branch release-2018 into master

Trivial conflict in checkpoint.cpp from fixing whether a return value
was ignored.

Change-Id: Ie2006eeee1118b32d1a46e47191db45b454a4ecd

diff --cc docs/CMakeLists.txt
Simple merge

diff --cc src/gromacs/ewald/pme-gpu-types.h
Simple merge

diff --cc src/gromacs/ewald/pme-spread.cu
Simple merge

diff --cc src/gromacs/ewald/pme.cu
Simple merge

diff --cc src/gromacs/ewald/pme.cuh
Simple merge

diff --cc src/gromacs/gmxpreprocess/topio.cpp
Simple merge

diff --cc src/gromacs/utility/coolstuff.cpp
Simple merge