Senility is a joy ride in the exultant, London-born revival of Tom Stoppard's 'Travesties,' which opened on Tuesday night at the American Airlines Theater. This account of a clash of three cultural titans - James Joyce, Vladimir Lenin and the Dadaist poet Tristan Tzara - in Zurich during World War I is related decades later by an ancient witness (one Henry Carr, of the British Consulate). His recollection is, to put it kindly, capricious.