Harry Potter’s Aunt Petunia is half-buried in the Earth. But hey, who isn’t? That, I’d say, is a fair reduction of Samuel Beckett’s 1961 Happy Days, a not-quite-monologue for a middle aged woman who is stuck in a rut, though really it seems to be more of a pool of slow-acting quicksand. And the woman playing The Woman — actually, she has a name; it’s Winnie — in the National Theatre of Great Britain…