`fromAscListXX` and `fromDistinctAscList` implemented
`fromDistinctAscList` improved
`fromDistinctAscList`: Tree replaced by array
`followPrefixesByteFrom` introduced
`fromDistinctAscList` rewritten using right one-hole context
`followPrefixesFrom` made strict
`fromAscListWithKey` imlemented using right one-hole context
`fromAscList_long` benchmark added