use tolerance


git-svn-id: https://geuz.org/svn/gmsh/trunk@19052 59c8cabf-10d6-4a28-b43f-3936b85956c4
access global lc in options


git-svn-id: https://geuz.org/svn/gmsh/trunk@19053 59c8cabf-10d6-4a28-b43f-3936b85956c4