exposed mesh functions that are needed to pass the vertex circulator unit tests

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1013 fdac6126-5c0c-442c-9429-916003d36597
finished the vertex-ihalfedge unit test and added the vertex-ohalfedge test

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1014 fdac6126-5c0c-442c-9429-916003d36597