resolv.rb: case-insensitive comparison

* lib/resolv.rb (Resolv::DNS::Name#==): DNS is case-insensitive, so the
  comparison should be case-insensitive as well.
  [ruby-core:66498] [Bug #10550]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49073 b2dd03c8-39d4-4d8f-98ff-823fe69b080e