The mystery of James L. Brooks’ Spanglish (Columbia, 12.17) will begin to unravel early next week. Is it Oscar material or just a (presumably) good relationship comedy? Will Tea Leoni’s performance hit the right notes or…? I keep thinking back to a report I heard several weeks ago, which is that Cloris Leachman, playing Leoni’s wine-drinking, acid-tongued mom, has all the zingers…