FRANKFURT, May 24 (Reuters) - The 100 millionth Volkswagen rolled off a German assembly line on Tuesday, taking the brand into an elite of four car companies whose output has stretched into nine digits, Europe's biggest carmaker said. The Touran compact van with a silver metallic paint job that set the milestone at VW's headquarters in Wolfsburg is only distantly related to the humble Volkswagen Beetle that became a global icon of affordable mobility after World War Two.