MAYBE I blinked and missed the credits. I know Johnny Depp and Christian Bale lead the cast of Public Enemies, but the name of the director charged with telling the tale of Depression-era criminal John Dillinger and his F.B.I. foil Melvyn Purvis escaped me. Ten minutes into the film -- after a prison break that should have kicked things into high gear with gunfire, blood and adrenaline -- I just wanted to know when it would end.