fix memory init problem

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/gridsvg@331 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
added pattern offset test

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/gridsvg@332 edb9625f-4e0d-4859-8d74-9fd3b1da38cb