By Corrie MacLaggan AUSTIN, Texas (Reuters) - Depeche Mode has come a long way since its 1980s debut as part of Britain's New Wave scene, and as it prepares to tour behind its 13th album, no one appears more surprised at the group's longevity than the band members themselves. The British synthpop pioneers - singer Dave Gahan, guitarist-keyboardist Martin Gore and keyboardist Andy Fletcher - are marking their fourth decade in the music industry with the release of "Delta Machine" on March 26. ...