Removed lots of warning introduced with my last commit, cleaned up a bit duplicateBoundaries, and introduced support for 2D for DuplicateBoundaries.

More cleanup is going to follow soon, especially in the modified part of commandline.

git-svn-id: https://geuz.org/svn/gmsh/trunk@19267 59c8cabf-10d6-4a28-b43f-3936b85956c4