TAPACHULA, Mexico (Reuters) -A dozen undocumented migrants on Mexico's southern border sewed their mouths shut on Tuesday in a bid to convince the country's immigration authority to grant them passage toward the U.S. border. The migrants, mostly Central and South Americans, helped each other seal their lips using needles and plastic threads, leaving a small space to consume liquids and using alcohol to wipe away drops of blood from the stitches, Reuters images show. “The migrants are sewing their lips together as a sign of protest," said Irineo Mujica, an activist at the demonstration. "We hope that the National Migration...