By Tim McLaughlin and Aaron Pressman BOSTON (Reuters) - Authorities are investigating whether the Boston Marathon bombing suspect who died after a shootout with police had any connection to an unsolved triple homicide in suburban Boston in 2011, a spokeswoman for prosecutors said on Monday. The 26-year-old Tamerlan Tsarnaev, identified by the FBI as one of two brothers suspected in last Monday's blasts, was a close friend of one of three men who were stabbed in the neck in an apartment in Waltham, Massachusetts in September, 2011. ...