addition to 'merge.R' script


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/opm@609 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
further improvements in 'merge.R' script


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/opm@610 edb9625f-4e0d-4859-8d74-9fd3b1da38cb