Billionaire investor William Ackman turned up the heat on Allergan Inc. on Thursday when he accused the Botox maker’s board of misleading investors to fend off a hostile takeover bid from Valeant Pharmaceuticals. Ackman, whose hedge fund Pershing Square Capital Management is Allergan’s biggest shareholder, told reporters that his lawyers had seen documents that show Allergan’s board knowingly released misleading statements about Valeant. They have lost about 6 percent in often volatile dealings since Valeant bid for Allergan in late April. Allergan’s shares edged up 0.7 percent.