name -> String[permalink][rdoc][edit]-
ルート要素名を返します。
document = REXML::Document.new(<<EOS) <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> EOS doctype = document.doctype p doctype.name # => "html"