--- Resolv::DNS#getresource(name, typeclass)
--- Resolv::DNS#getresources(name, typeclass)
--- Resolv::DNS#each_resource(name, typeclass) {|resource| ...}
    They lookup DNS resources of name.
    name must be a instance of Resolv::Name or String.

    typeclass should be one of follows:
    * Resolv::DNS::Resource::IN::ANY
    * Resolv::DNS::Resource::IN::NS
    * Resolv::DNS::Resource::IN::CNAME
    * Resolv::DNS::Resource::IN::SOA
    * Resolv::DNS::Resource::IN::HINFO
    * Resolv::DNS::Resource::IN::MINFO
    * Resolv::DNS::Resource::IN::MX
    * Resolv::DNS::Resource::IN::TXT
    * Resolv::DNS::Resource::IN::ANY
    * Resolv::DNS::Resource::IN::A
    * Resolv::DNS::Resource::IN::WKS
    * Resolv::DNS::Resource::IN::PTR
    * Resolv::DNS::Resource::IN::AAAA

    Lookupped resource is represented as an instance of (a subclass of)
    Resolv::DNS::Resource.

