[2656] Add CNAME implementation

src/lib/dns/gen-rdatacode.py.in

@@ -33,6 +33,7 @@ import sys
 # Example:
 #     new_rdata_factory_users = [('a', 'in'), ('a', 'ch'), ('soa', 'generic')]
 new_rdata_factory_users = [('aaaa', 'in'),
+                           ('cname', 'generic'),
                            ('hinfo', 'generic'),
                            ('naptr', 'generic'),
                            ('mx', 'generic'),

src/lib/dns/rdata/generic/cname_5.cc

@@ -39,6 +39,11 @@ CNAME::CNAME(InputBuffer& buffer, size_t) :
     // check consistency.
 }
 
+CNAME::CNAME(MasterLexer& lexer, const Name*, MasterLoader::Options,
+             MasterLoaderCallbacks&) :
+    cname_(lexer.getNextToken(MasterToken::QSTRING).getString())
+{}
+
 CNAME::CNAME(const CNAME& other) :
     Rdata(), cname_(other.cname_)
 {}