Export two functions to handle pixmap objects in s.logo

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/ade4@672 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Update the default color of polygons

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/ade4@673 edb9625f-4e0d-4859-8d74-9fd3b1da38cb