BIND 10 #2382: introduce generic version of rdata::createRdata(text)

[BIND 10 Development]

#2382: introduce generic version of rdata::createRdata(text)
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |  UnAssigned
            Priority:  medium        |                       Status:  new
           Component:  libdns++      |                    Milestone:  New
           Sensitive:  0             |  Tasks
         Sub-Project:  DNS           |                     Keywords:
Estimated Difficulty:  0             |              Defect Severity:  N/A
         Total Hours:  0             |  Feature Depending on Ticket:
                                     |  loadzone-ng
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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 Subtask of #2368, depend on #2374 (and slightly #2377), and,
 effectively, depend on many other tickets that implement this version
 for actual derived classes.

 The signature would look like this:

 {{{#!cpp
 ConstRdataPtr createRdata(const RRType& rrtype, const RRClass& rrclass,
                           MasterLexer& lexer, const Name* origin,
                           MasterLoader::Option options,
                           MasterLoader::Callbacks& callbacks);
 }}}
 Parameter semantics should be mostly obvious.  `origin` may need an
 explanation: it may need for some RDATA that have domain name field
 and its text isn't absolute.

 Like the current version, it'll be basically a wrapper of actual
 derived class methods.  But see also BIND 9's
 lib/dns/rdata.c:dns_rdata_fromtext().  It has some other checks,
 so we may have to do similar things.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2382>
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