use step(a, 1) to prevent rounding of step value to zero is smaller than 1e-10


git-svn-id: https://geuz.org/svn/gmsh/trunk@18505 59c8cabf-10d6-4a28-b43f-3936b85956c4
script from Arthur Levy


git-svn-id: https://geuz.org/svn/gmsh/trunk@18506 59c8cabf-10d6-4a28-b43f-3936b85956c4