For on his way outjust before he heartily bussed several diplomats wiveshe met the press. Chiding an American newsman for knowing so littl6 of Russia. he was instantly reminded that Russia has long excluded many correspondents. Khrushchev. lurching a bit. generously promised visas to all correspondents within earshot. Nevt day 13 applications went in. The strange part of the story is that within a week six of the visas had been approved and approval was promised for the rest. Much has been said about prying open the Iron Curtain. but nobody ever suspected that it might jerk upward some day to make good an alcoholic boast. Is that what is happening?