Harry Shearer, increasingly the sonorous voice of protest in various contract disputes, is suing the entertainment groups Vivendi and StudioCanal for $125 million , over profits he says he was cheated out of for This Is Spinal Tap . Shearer played Derek Smalls, bassist and self-described “lukewarm water,” in the 1984 metal mockumentary, which was based on characters he, Christopher Guest, and …