AH, YOUTH! Being “of a certain age” I’ve often observed facetiously that the world is 28 years old. At the August Wilson Theatre there is no better proof of that than the audience, which delights -almost cultishly - to the musical version of the 2004 teen comedy movie MEAN GIRLS. When the film was released, the target audience for this musical was in the adolescent throes of high school, which is the topic of MEAN GIRLS , or, as a pair of high school nerds Janis and Damien