What's going on in our theatres? A recent spate of rowdy behaviour " notably at jukebox musicals " raises the question: have audiences simply forgotten how to behave? A drunk woman in the seat next to me is softly caressing my hair as though stroking the ears of a particularly mild-mannered spaniel. It's a strange sensation, but I can't really complain because I'm at the theatre. You're not meant to talk. Just as I r…