WANA, Pakistan (Reuters) - A suspected U.S. missile strike on a Pakistani madrasa near the Afghan border killed six people on Monday, possibly including an al Qaeda chemical and biological weapons expert, Pakistani security officials said. A senior Pakistani security official said Abu Khabab al-Masri, an Egyptian chemist regarded as one of al Qaeda's top bomb makers, could have been the target. Monday's pre-dawn attack blitzed a house close to a madrasa used by militants near Azam Warsak village, about 20 km (12 miles) west of Wana, the main town of the South Waziristan tribal region, a known hotbed of...