By Suleiman Al-Khalidi AMMAN (Reuters) - France said on Tuesday it had performed tests that proved President Bashar al-Assad's forces had used nerve gas in Syria's civil war, a "red line" that the United States and other countries have repeatedly said would demand a response. Washington separately said it would deploy Patriot missiles and F-16 fighter jets to Syria's neighbor Jordan for a military exercise and perhaps longer. Russia, Assad's main international backer, criticized the move and accused the West of inflaming the conflict by sending arms to the war zone. ...