HCELL_INDEX
CmpAddToLeaf(
      PHHIVE Hive,
      HCELL_INDEX LeafCell,
      HCELL_INDEX NewKey,
      PUNICODE_STRING NewName
  );

Routine Description:

    Insert a new subkey into a Leaf index. Supports both fast and slow
    leaf indexes and will determine which sort of index the given leaf is.

    NOTE:   We expect Root to already be marked dirty by caller if non NULL.
            We expect Leaf to always be marked dirty by caller.

Arguments:

    Hive - pointer to hive control structure for hive of interest

    LeafCell - cell of index leaf node we are to add entry too

    NewKey - cell of KEY_NODE we are to add

    NewName - pointer to unicode string with name to we are to add

Return Value:

    HCELL_NIL - some resource problem

    Else - cell of Leaf index when are done, caller is expected to
            set this into Root index or Key body.