bdlcc_skiplist: 'removeAll' zeroing out 'd_next_p' in nodes (#3447)
bdlcc_skiplist: 'removeAll' zeroing out 'd_next_p' in nodes (#3447)

* bdlcc_skiplist: 'removeAll' zeroing out 'd_next_p' in nodes

* bdlcc_skiplist: add asserts
bloomberg/bde,bloomberg/bde,bloomberg/bde,bloomberg/bde,bloomberg/bde