June 25 (Reuters) - Some U.S. oil and gas producers in the Gulf of Mexico began restarting production and restaffing evacuated platforms on Monday as Tropical Storm Debby, the first named storm of the 2012 Atlantic hurricane season to hit the Gulf and disrupt operations, headed northeastward toward Florida. The U.S. Bureau of Safety and Environmental Enforcement said Monday that 44.1 percent of the Gulf's oil output and 34.8 percent of natgas production per day were shut in. As restarts prog