BIND 10 #2433: implement validateZone, base part

[BIND 10 Development]

#2433: implement validateZone, base part
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |  jinmei
            Priority:  medium        |                       Status:
           Component:  libdns++      |  accepted
            Keywords:                |                    Milestone:
           Sensitive:  0             |  Sprint-20130108
         Sub-Project:  DNS           |                   Resolution:
Estimated Difficulty:  4             |                 CVSS Scoring:
         Total Hours:  0             |              Defect Severity:  N/A
                                     |  Feature Depending on Ticket:
                                     |  loadzone-ng
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Comment (by jinmei):

 trac2433 is ready for review.

 I believe the implementation is straightforward.  It's also generally
 compatible with what BIND 9 does (with some notable exceptions -
 see the documentation).

 Some additional notes:
 - I used this opportunity to introduce a separate header file for
   a set of forward declarations.  This is unrelated and independent
   change, but I believe we need something like this sooner or later
   (and using something like this is more appropriate outside of
   libdns++)
 - the copyright year for the new files is correct; I started editing
   them within 2012.
 - I decided to change the name from "validate" to "check" since the
   former is also used in the context of DNSSEC validation and could be
   confusing.
 - I expect we'll want to introduce a class for more complete checks
   (subject of a separate task) instead of a free function.  I
   considered an option to define the basic version as part of such
   class, but at the moment I chose not to as it's not really clear
   yet.
 - there's one possible point of change depending on the final form of
   #2432.  As I commented in
   http://bind10.isc.org/ticket/2432#comment:26
   the return value of find() may be changed.  In that case we need to
   make trivial corresponding change to this branch.  But it shouldn't
   change the overall structure of the branch.

 Finally, regarding changelog: it may make sense to provide an entry
 for this as this API is expected to be used for others (too).  But
 other APIs that are equally important aren't explicitly mentioned
 either, so I opted not to add it for this.  We may want to mention the
 API update in a meta entry later, when we complete other related
 tasks.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2433#comment:10>
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