Audi is pulling out its biggest gun yet for the Beijing Motor Show, and while the big news for the A8 L might be the 6.3-liter W12 and the sedan's longer wheelbase, it's the rear seat accommodations that have us frothing at the mouth.Seriously, just look at it.With an overall length of nearly 17 and a half feet, the A8 L is almost a half-foot longer than its standard sibling, with a wheelbase of