BIND 10 #2086: allow construct LabelSequence from "raw data"

[BIND 10 Development]

#2086: allow construct LabelSequence from "raw data"
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |  UnAssigned
            Priority:  medium        |                       Status:  new
           Component:  libdns++      |                    Milestone:  Next-
           Sensitive:  0             |  Sprint-Proposed
         Sub-Project:  DNS           |                     Keywords:
Estimated Difficulty:  0             |              Defect Severity:  N/A
         Total Hours:  0             |  Feature Depending on Ticket:
                                     |  scalable inmemory
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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 i.e. sets of const uint8_t* data (for name data and offsets).

 We first need to make this class free from Name object (so directly
 holding a uint8_t*  of name data and offsets).  Then add another
 constructor to make this ticket possible.

 One open question is how much we should validate its input.  basically
 the data should originally come from another LabelSequence and should
 be valid.  But it's not guaranteed by the interface, so it should be
 generally validated.  But it could be expensive in the intended usage
 of it - we should consider the tradeoff.

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Ticket URL: <http://bind10.isc.org/ticket/2086>
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BIND 10 Development