Feature refix ZK-1856: Tree support frozen as grid
http://tracker.zkoss.org/browse/ZK-1856
Merge branch 'master' of https://github.com/zkoss/zk into F70-ZK-1856
Merge branch 'master' of https://github.com/zkoss/zk into F70-ZK-1856
Merge branch 'master' of https://github.com/zkoss/zk into F70-ZK-1856
Merge branch 'master' of https://github.com/zkoss/zk into F70-ZK-1856
Fix Treechildren.invalidate() problem and refixed ZK-1856: Tree support frozen as grid
Merge branch 'F70-ZK-1856' of git://github.com/huangnoah/zk