By CECILIA RAZAKYou might remember The Day The Earth Stood Still as that hokey, if well-meaning, sci-fi message-movie from the 1950's. (And if you do remember it, chances are the title also describes the day you shouted ''Klaatu barado nikto!'' at your gym teacher.) But for all those who haven't seen the original, or think it lacked explosions and/or terrorism subplots: Keanu Reeves, Jennifer Connelly and Jon Hamm have the new movie for you!The new version of the old classic comes out Friday, an