Walter Cronkite has agreed to do a three-day stint teaching journalism students at the University of Texas. The former CBS anchorman will address 34 students in the senior fellows program Oct. 17-19. Cronkite attended the university before becoming a correspondent for the Houston Post in 1937 and later for United Press and CBS. While in Austin, Cronkite is expected to announce he is donating some 500 boxes of his personal papers and memorabilia to the university. And that's the way it is.