gmx xpm2ps needs minor revision for gromacs version > 5.1
This is a minor issue for high gromacs version, such as 2016, 2018, 2019, 2020, 2021...
Default behavior for these version of gmx xpm2ps generated a bad eps file, whith ugly axis label.
The code line https://gitlab.com/gromacs/gromacs/-/blob/master/src/gromacs/gmxana/gmx_xpm2ps.cpp#L174, this defalut x-major value is 1, so for many xpm file will generete ugly label beause program can not determine tick spacing automatically, so must set it to <=0.
Although we can provide ps.m2p manually for gmx xpm2ps, but it is hard to set appropriate parameters for many users. So I still suggest set it to 0 in this code as default value, same as v5.1 or before. @acmnpv