democratic presidential candidates hillary clinton bernie sanders wednesday cheer end u.s. drugmaker pfizer inc pfe.n 160 billion merger ireland-based allergan plc agn.n glad hear pfizer call merger need close loopholes let corporations escape pay tax clinton say twitter sanders say social media site applaud president barack obama new rule aim curb so-called inversion deal pfizer say lead scrap deal democratic white house hopefuls cheer end pfizer allergan deal