fails:IO.for_fd raises an error if passed matching binary/text mode two ways
fails:IO.for_fd raises an error if passed conflicting binary/text mode two ways
windows:IO.for_fd raises an Errno::EINVAL if the new mode is not compatible with the descriptor's current mode
fails:IO.for_fd ignores the :encoding option when the :external_encoding option is present
fails:IO.for_fd ignores the :encoding option when the :internal_encoding option is present
fails:IO.for_fd accepts options as keyword arguments
