instruct! (Builder::XmlMarkup)

    # File lib/active_support/vendor/builder-2.1.2/builder/xmlmarkup.rb, line 238
        def instruct!(directive_tag=:xml, attrs={})
          _ensure_no_block block_given?
          if directive_tag == :xml
            a = { :version=>"1.0", :encoding=>"UTF-8" }
            attrs = a.merge attrs
          end
          _special(
          "<?#{directive_tag}",
          "?>",
          nil,
          attrs,
          [:version, :encoding, :standalone])
        end