There’s a reason every one of us can pronounce “supercalifragilisticexpialidocious.”It’s no mere happenstance that we know the words to the musical numbers from “Mary Poppins” — “A Spoonful of Sugar,” “Chim Chim Cher-ee,” “Let’s Go Fly a Kite” — as well as we know “The Star-Spangled Banner.”The score of the 1964 supernanny classic is unforgettable. The movie’s star, Julie Andrews, had a big Broadway voice and each of …