AMMAN (Reuters) - A Syrian missile killed at least 20 people in a rebel-held district of Aleppo on Tuesday, opposition activists said, as the army turns to longer-range weapons after losing bases in the country's second-largest city. The use of what opposition activists said was a large missile of the same type as Russian-made Scuds against an Aleppo residential district came after rebels overran army bases over the past two months from which troops had fired artillery. ...