BIND 10 #2106: allow RBTree::find to take LabelSequence

[BIND 10 Development]

#2106: allow RBTree::find to take LabelSequence
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |                       Status:  new
            Priority:  medium        |                    Milestone:  Next-
           Component:  data source   |  Sprint-Proposed
           Sensitive:  0             |                     Keywords:
         Sub-Project:  DNS           |              Defect Severity:  N/A
Estimated Difficulty:  0             |  Feature Depending on Ticket:
         Total Hours:  0             |  scalable inmemory
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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 i.e., define this:

 {{{#!cpp
 template <typename T>
 template <typename CBARG>
 typename RBTree<T>::Result
 RBTree<T>::find(const dns::LabelSequence& target_labels,
                 RBNode<T>** target,
                 RBTreeNodeChain<T>& node_path,
                 bool (*callback)(const RBNode<T>&, CBARG),
                 CBARG callback_arg) const
 }}}

 Actually, the current version (taking `Name`) will then be a trivial
 wrapper for this version.

 We'll need this if we encode RDATA names as name+offset data, instead
 of pointers to tree nodes for additional record handling (otherwise
 we'll need to do expensive construction of `Name` object).

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Ticket URL: <http://bind10.isc.org/ticket/2106>
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BIND 10 Development