BAGHDAD, Jan 2 (Reuters) - Thousands of Sunni Arabs vented their anger on Tuesday over Saddam Hussein's execution as the Iraqi government promised an investigation into illicitly filmed footage of Shi'ite officials taunting him on the gallows. A court official said he nearly halted the hanging over the jeering, which has inflamed sectarian passions in a nation already on the brink of civil war. Data showed civilian deaths hit a new record in December and were over 12,000 in 2006. He also challenged government claims those who filmed the event were guards, saying they were senior officials. In the video,...