add (REXML::Document)

    # File rexml/document.rb, line 53
      def add( child )
    			if child.kind_of? XMLDecl
    				@children.unshift child
    			elsif child.kind_of? DocType
    				if @children[0].kind_of? XMLDecl
    					@children[1,0] = child
    				else
    					@children.unshift child
    				end
    			else
    				rv = super
    				raise "attempted adding second root element to document" if @elements.size > 1
    				rv
    			end
    		end