Checkbox Tree Flags

**Checkbox Tree Flags**
constant	meaning
`NEWT_CHECKBOXTREE_UNSELECTABLE`
`NEWT_CHECKBOXTREE_HIDE_BOX`
`NEWT_CHECKBOXTREE_COLLAPSED`
`NEWT_CHECKBOXTREE_EXPANDED`
`NEWT_CHECKBOXTREE_UNSELECTED`
`NEWT_CHECKBOXTREE_SELECTED`