Task #2831: Bump required version numbers of infrastructure for 2020
increase cmake reqirement for GROMACS 2020
As in #2012, we should look at both benefits of updating to newer infrastructure, and to minimize the impact on users through understanding which likely production distros have what package available in January 2019. Data below gathered in May 2018.
Available is preferably "available natively in a fresh installation" but since anyway one often needs recent CUDA, or drivers, or compilers, we consider it acceptable if the necessary cmake version can be obtained easily through standardized backports/upgrades repositories. Remember also that Kitware provides high quality binary packages for download, and cmake self-bootstraps beautifully from source from whatever c++ compiler and make is present on the system. So it is never likely for installing cmake to be intrinsically hard, nor harder than anything else needed to install GROMACS for production use.
Possible production distros:
Centos 7: 2.8.11 (but 3.11.0 available in Fedora EPEL 7)
Fedora 28: 3.11.0
Ubuntu 16.04 (xenial): 3.5.1
Ubuntu 18.04 (bionic): 3.10.2
Debian stable (stretch) : 3.7.2 (but 3.9.5 available in stretch-backports)
FreeBSD 11.1: 3.8.1 (but 3.11.1 available in freshports)
Rolling distros won't generally be an issue, but:
arch linux 3.11.1
gentoo 3.9.6 and everything more recent
cmake 3.8 has native CUDA support (which removes the need for FindCUDA and current work-arounds)
cmake 3.9 adds native CUDA support also on Visual Studio (but needs CUDA 8.0.61)
cmake 3.9 adds a GoogleTest module, improves FindDoxygen, adds CheckIPOSupported (gcc and clang), adds CUDA_PTX_COMPILATION property
cmake 3.9 improves mac rpath handling by default (https://cmake.org/cmake/help/v3.9/policy/CMP0068.html)
Require cmake 3.9.6
Allows to use modern OpenMP support. The change will permit further
simplifications and modernization, particularly for CUDA.
Also bump release matrices to conform to new requirements.