remove lme4 dependency

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/r2mlwin@248 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
claim external functions used in the package

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/r2mlwin@249 edb9625f-4e0d-4859-8d74-9fd3b1da38cb