FULBRIGHT'S UPCOMING TRIP TO EUROPE, GREECE; CYPRUS; UK TRADE WITH CUBA; LBJ'S MEETING WITH R. A. BUTLER; FULBRIGHT'S CONCERN RICHARD RUSSELL, PRESS WILL SEE HIS TRIP AS WAY TO AVOID CIVIL RIGHTS BILL CLOTURE VOTE; FULBRIGHT'S VIEWS ON CIVIL RIGHTS BILL