Stock futures plowed higher ahead of Thursday's open, bolstered by solid action overseas and by generally positive economic reports. Dow futures were up 65 points and rising. Nasdaq futures were up 18.25 points and also pointed higher. S&P 500 futures held a 7.9 point advance. Initial jobless claims dipped 5.5% to 393,000 in the week ended Nov. 24, the Labor Department reported. That was short of the slowdown to 390,000 claims projected by