Testing landing-on-slope

While reviewing the "tiled" chapter produced by my blogpress tools, I remembered that landing on a slope still produces odd effects from time to time. And then came an idea to reproduce these conditions in the unit-test environment. Just as I was observing that the "dkp54" branch has been around from a long time and so has been the "cflags" branch and that "right, I promised myself I wouldn't…