BIND 10 #2111: Define a dedicated result context and additional record handling.

[BIND 10 Development]

#2111: Define a dedicated result context and additional record handling.
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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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 This is a revised version of current `RBNodeResultContext`
 and `InMemoryZoneFinder::Context`.  But right now additional shortcut
 is not available, so it's actually pretty simple.

 Iterate over each RDATA of the given RRset using the encoded version
 of iterator, and use findNode() to get the node for each name field of
 the RDATA whose attribute indicates additional handling is needed.
 Then go through the nodes' `RdataSet` to find specified type of data.
 Construct `TreeNodeRRset` for them and push them to the result.

 One open question is whether we should distinguish "glue ok" case or
 not.  I'm now inclined to skip this differentiation, but we can
 discuss it.

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Ticket URL: <http://bind10.isc.org/ticket/2111>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development