The question of whether or not David McCallum and his wife Jill would mend their marriage was settled when Jill went to court, sued for divorce, and asked for custody of the three little McCallums, and "all community property," and that seemed to be that.  At the time, McCallum said nothing. He only wanted to talk about the new Girl From U.N.C.L.E. series, of which he disapproved.  "A second show with the same super agent theme is just too much," said David.  "It has to dilute our own audience" (David was right. The Man From U.N.C.L.E. was diluted and The Girl From U.N.C.L.E. was fired after one season).  "I'm surrounded by my bread and butter," he said, somewhat mysteriously.  What did not seem mysterious was the feeling David had developed for a beautiful dark-haired model named Kathy Carpenter, who's heavily favored to become the next Mrs. McCallum.  "David's the faithful type, he's not a flitter," says one of David's associates, and certainly David and Kathy have become inseparable.  He even took her off on his tour of Japan, and he had her share the spotlight and the mikes when he was interviewed by the press (left) which is no way to keep their names out of the papers, and if you look back on his recent testimony from Italy, you realize David just doesn't care.  "Kathy and I are getting very Italian," he told one magazine reporter in Portofino.  "We went out to eat late last night and didn't get to bed until 4 A.M."  Things are just as hectic and just as romantic in Japan.  At this writing it looks as though David won't stay single for long.