waylandloginmanager: use pixman for the loginmanagerdisplay. It's more likely to work on all hardware, as some platfoms have mesa issues

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@2476 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9
Add a pixman Weston session

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@2477 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9