Cache `Column.dirty` property, by Francesc.
Cache `Column.dirty` property, by Francesc.


git-svn-id: 92c705c98a17f0f7623a131b3c42ed50fcde59b4@1691 1b98710c-d8ec-0310-ae81-f5f2bcd8cb94

PyTables/PyTables,andreabedini/PyTables,rabernat/PyTables,andreabedini/PyTables,cpcloud/PyTables,andreabedini/PyTables,rabernat/PyTables,gdementen/PyTables,mohamed-ali/PyTables,joonro/PyTables,rdhyee/PyTables,tp199911/PyTables,PyTables/PyTables,FrancescAlted/PyTables,avalentino/PyTables,gdementen/PyTables,jack-pappas/PyTables,tp199911/PyTables,tp199911/PyTables,andreabedini/PyTables,dotsdl/PyTables,avalentino/PyTables,rdhyee/PyTables,rdhyee/PyTables,avalentino/PyTables,jennolsen84/PyTables,cpcloud/PyTables,FrancescAlted/PyTables,jack-pappas/PyTables,tp199911/PyTables,dotsdl/PyTables,gdementen/PyTables,dotsdl/PyTables,rabernat/PyTables,jennolsen84/PyTables,jack-pappas/PyTables,cpcloud/PyTables,joonro/PyTables,PyTables/PyTables,joonro/PyTables,mohamed-ali/PyTables,jack-pappas/PyTables,jack-pappas/PyTables,jennolsen84/PyTables,dotsdl/PyTables,mohamed-ali/PyTables,rdhyee/PyTables,jennolsen84/PyTables,FrancescAlted/PyTables,gdementen/PyTables,rabernat/PyTables,cpcloud/PyTables,joonro/PyTables,mohamed-ali/PyTables