* lib/drb/drb.rb: use attr_reader instead of Module#attr.
  [Feature #10172][ruby-core:64582]
* lib/irb/ruby-token.rb: ditto.
* lib/net/telnet.rb: ditto.
* lib/rdoc/ruby_token.rb: ditto.
* lib/thwait.rb: ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47298 b2dd03c8-39d4-4d8f-98ff-823fe69b080e