git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_1@25546 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merges r24679 from trunk into ruby_1_9_1.¶
dupped or frozen, because freezing it causes #concat method failure,
and unnecessary to dup without freezing. a patch from Aaron
Patterson at [ruby-core:25145].
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_1@25546 b2dd03c8-39d4-4d8f-98ff-823fe69b080e