A red-band trailer of Tropic Thunder, releasing August 15 from Paramount/DreamWorks, has now gone live online, and it’s a nice, short piece of gung-ho war parody, even if all it does is basically slap up costumed pictures of the cast and have them yell and/or fire a weapon. Be advised, though, that you’ll have to access the stumper question of your birth date. Tricky, that…