Gene Maddaus Senior Media WriterThom Davis, the longtime head of IATSE Local 80, announced on Sunday that he will be stepping down at the end of the year, a local official told Variety.Davis, who has served as business manager since 1998, was a strong supporter of the new IATSE Basic Agreement, which was narrowly approved by the 13 West Coast IATSE locals in an unusually contentious vote last month.