Added compress.val option to tabfreq so that user can specify which level of y to show for binary x and y. Also changed print() to message() in tabmeans and tabfreq so that it is easier to block in LaTeX.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/tab@43 edb9625f-4e0d-4859-8d74-9fd3b1da38cb