The Dog Stars by Peter Heller Knopf, $24.95, 320 pages, ISBN 978-0-307-95994-2 Woof-woof-woof.  There’s an old saw that goes like this:  You can’t teach an old dog new tricks, that I learned from my mother’s mother when I was just a little boy.  Superstitious to the end, “Nanny,” as Grandma O’Toole was called, set store by it and many others like it. Well . . . without any disrespect