First lady yuks it up with correspondents / Laura Bush steals show from president -- and uses humor to humanize her husband: "Judging from the laughter in the Washington Hilton ballroom at her words -- 'George's answer to any problem at the ranch is to cut it down with a chain saw, which I think is why he and (Dick) Cheney and (Donald) Rumsfeld get along so well' -- Laura Bush has a future in political stand-up comedy. "