TIdDNSResolver update

A user recently needed to query a DNS server for DNAME records, but found that TIdDNSResolver did not parse DNAME answers at all. The QueryResult collection would hold generic TResultRecord objects that did not have their RecType property assigned properly, so it would default to 0, which just happens to be qtA.

So, a new TDNAMERecord class has been added for parsing DNAME records, and its RecType property will be set to qtDName.

There are quite a number of DNS record types that TIdDNSResolver still does not parse. When creating a generic TResultRecord object for these record types, its RecType property will now be assigned a value from the TQueryRecordTypes enum, if one has been defined. For other unknown record types, a new TypeCode property has been added to the TResultRecord class to hold the actual type number that is reported by DNS.