“Fatman,” the “Santa Claus versus contract killer” action-comedy-fantasy movie from brothers Eshom and Ian Nelms, dares to wonder just how in the hell Saint Nicholas can afford to produce enough toys to reward every child in the world for good behavior? No one cares about the logistics of his once-a-year globe trot; it’s magic. But in “Fatman,” rather than a portly and jovial old wizard, Santa’s a worn down sodbuster working his fingers to the bone to keep the doors open on his workshop at a moment where more kids end up on the naughty list than ever, and his government subsidy doesn’t cover annual shortfalls. It’s a tough time to be jolly.