Michael Douglas is recounting what his close pal Jack Nicholson would give him a hard time about back in the day. “[The character’s] hair has always been an important part of my acting,” the “China Syndrome” actor, 81, explained during a Q&A before a screening of his 1987 film “Wall Street” last month. “It’s just funny how that kind of thing helps.” “Jack Nicholson always used to give me sh–t about hair acting. [He’d say], ‘What’s with his hair acting?’ I said, ‘You should talk,’” Douglas