Preparing tests for DDM waveguide

git-svn-id: https://geuz.org/svn/gmsh/trunk@20146 59c8cabf-10d6-4a28-b43f-3936b85956c4
git-svn-id: https://geuz.org/svn/gmsh/trunk@20147 59c8cabf-10d6-4a28-b43f-3936b85956c4