BIND 10 #1607: define ZoneFinder::findAdditional() and implement its default version

[BIND 10 Development]

#1607: define ZoneFinder::findAdditional() and implement its default version
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                   Reporter:         |                 Owner:  jinmei
  jinmei                             |                Status:  accepted
                       Type:  task   |             Milestone:
                   Priority:  major  |  Sprint-20120306
                  Component:         |            Resolution:
  b10-auth                           |             Sensitive:  0
                   Keywords:         |           Sub-Project:  DNS
            Defect Severity:  N/A    |  Estimated Difficulty:  4
Feature Depending on Ticket:  auth   |           Total Hours:  0
  performance                        |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Comment (by jinmei):

 trac1607 is ready for review.

 I've extended the scope of this ticket as discussed on the dev list.
 See the one with the subject of "proposal: a performance extendable
 auth query logic framework".

 Unfortunately the amount of diff is big (again...), but hopefully it's
 not as bad as it might look; most part of the changes are
 straightforward refactoring due to the interface change.

 - the first two commits are relatively straightforward refactoring but
   the diff is big, so it's probably better to review these separately.
 - 118f1f9 and ac29935 are unrelated extension for test utility and can
   be reviewed separately.
 - from 4bcec5f to 1633572 (excluding 118f1f9 and ac29935) are the main
   changes for this branch.
 - 29fab38 and 6f31530 are updates to the auth::Query class due to the
   interface change.  I believe these are straightforward.
 - 64611b9 is an unrelated optimization.  If it looks too out-of-scope
   I'm okay with excluding it.

 This is the proposed changelog entry:
 {{{
 392.?   [func]*         jinmei
         libdatasrc: change the return type of ZoneFinder::find() so it can
         contain more context of the search, which can be used for
         optimizing post find() processing.  A new method getAdditional()
         is added to it for finding additional RRsets based on the result
         of find().  External behavior shouldn't change.  The query
         handling code of b10-auth now uses the new interface.
         (Trac #1607, git TBD)
 }}}

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Ticket URL: <http://bind10.isc.org/ticket/1607#comment:7>
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