Spring spells love, and love spells torment, longing, becoming undone. You'll feel it sharply in these films, whether in the collision between Cher and Nicolas Cage in "Moonstruck" or in two-thirds of Richard Linklater's "Before" trilogy, where a single day of conversation between two strangers begins an 18-year love story. And then there are the fantasies-turned-terrors of Michael Haneke's "The Piano Teacher" (well, maybe these movies aren't all about love).