onelab::server.isRegistered(client), path checking tool, reorganised call to the preprocessor

git-svn-id: https://geuz.org/svn/gmsh/trunk@20109 59c8cabf-10d6-4a28-b43f-3936b85956c4
git-svn-id: https://geuz.org/svn/gmsh/trunk@20110 59c8cabf-10d6-4a28-b43f-3936b85956c4