Sean Stone, son of Oliver Stone, is a chip off the old block. Sean, 25, took time off from college to make a documentary on his dad’s struggle to make “Alexander” in 2004. Now, he’s directing his own first feature, “Shadowland,” a “Blair Witch Project”-like movie about the mental hospital where Rosemary Kennedy was lobotomized. Sean, who appeared in his dad’s “JFK,” stars in “Shadowland,” in which Oliver also appears as his father. Monique van Vooren, who had a part in Oliver’s first film, “Sugar Cookies” (1973), also has a part in Sean’s project.