DON'T MISS the Huntington Theatre Company's "RIPCORD" which just opened at the Calderwood Pavilion and has already been extended through July 2! David Lindsay-Abaire's comedy is set in that most hilarious and freewheeling of all environments--an assisted living complex. Hang on, it involves two elderly women who find themselves roommates, but one of them can't stand the other. The sour-pussed Abby (Nancy E. Carroll)