“Coming soon to German cinemas: a demoralized, drug-addled Adolf Hitler who plays with a toy battleship in the bathtub, dresses his dog in a Nazi uniform and takes acting tips from a Jewish concentration camp inmate. The movie, which opens Jan. 11, is treading ground that once would have been off-limits. This is not Mel Brooks’ ‘The Producers’ or Charlie Chaplin’s ‘The Great Dictator,’ but a German movie that dares to treat Hitler as comedy.”