fix last commit

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/coin@878 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
unused levels in 'block' wasn't allowed

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/coin@879 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
it is now an error to supply four- or higher-way tables

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/coin@880 edb9625f-4e0d-4859-8d74-9fd3b1da38cb