def unescape_form(str)
      str = str.dup
      binary_encode(str)
      str.gsub!(/\+/, ' ')
      str.gsub(ESCAPED) { $1.hex.chr }
    end
def unescape_form(str)
      str = str.dup
      binary_encode(str)
      str.gsub!(/\+/, ' ')
      str.gsub(ESCAPED) { $1.hex.chr }
    end
Unescape form encoded values in +str+