Ruby

io.c: try to_io first

• io.c (copy_stream_body): try to_io conversion before read,
  readpartial, and write methods. [ruby-dev:49008] [Bug #11199]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52750 b2dd03c8-39d4-4d8f-98ff-823fe69b080e