It was maybe four songs into the Offspring's set -- somewhere around "Days Go By" and "Have You Ever," that the message became clear: Purists be damned. Frontman Dexter Holland looks every bit of his 46 years, and if his band didn't want to play punk music in its unvarnished, long-since formulated form, then goddamn it, they wouldn't. Last night's Offspring concert attempted to cover the generational and stylistic gap between its indisputably over-thirty fanbase and the kids young enough to be their own, uh, offspring. The results were mixed.