AMMAN (Reuters) - Syrian rebels killed 23 government soldiers on Monday, activists said, and efforts to find a viable political alternative to Bashar al-Assad faltered when an opposition group said it would boycott Arab-backed talks to unite its splintered ranks. The latest bloodshed centered in the town of Rastan, where opposition sources said President Assad's forces killed nine other people, further unraveling a month-old U.N. ceasefire pact that is being overseen by international monitors. ...