It seems like the axis (and grid) restriction has been lifted in 2.8. You can now toggle those on and off in ortho view.
However for some reason the z axis didn't get this restriction lifted, so you could toggle the X/Y axis on and off in ortho view, but not the Z axis.
I also noticed that the grid_lines (or gridlines) variable doesn't seem to be used anymore (as the grid is infinite in the 3d view now).
However, I didn't remove it as I'm not sure if this will break older blend files or not. Can I simply remove it from source/blender/makesdna/DNA_view3d_types.h and the rest of the remaining places in the code?