In “Hugo,’’ an exhilarating tale of magic, machines, memories, and dreams, Martin Scorsese pulls off the neatest trick of all. He marshals the marvels of modern movie technology - up to and including the dreaded 3-D - to create a love letter to the earliest of movies and, by extension, to every movie from then to now. Yes, “Hugo’’ is a family film and, yes, your children and your inner child stand to be enraptured, but the family Scorsese really made this for is the 100-year-old tribe of watchers in the dark.