add_attributes_to

# File lib/rdoc/ri/formatter.rb, line 327
  def add_attributes_to(txt)
    tokens = txt.split(%{(</?(?:b|code|em|i|tt)>)})
    text = AttributeString.new
    attributes = 0
    tokens.each do |tok|
      case tok
      when %{^</(\w+)>$} then attributes &= ~(ATTR_MAP[$1]||0)
      when %{^<(\w+)>$}  then attributes  |= (ATTR_MAP[$1]||0)
      else
        tok.split(//).each {|ch| text << AttrChar.new(ch, attributes)}
      end
    end
    text
  end