* lib/resolv.rb (Resolv::IPv6.create): avoid modifying frozen

	* test/resolv/test_dns.rb (test_ipv6_create): test for above
	  [Bug #11910] [ruby-core:72559]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@54404 b2dd03c8-39d4-4d8f-98ff-823fe69b080e