On the first day of the 2015 ABN AMRO World Tennis Tournament in Rotterdam, Grigor Dimitrov saved two match points to defeat Paul-Henri Mathieu, 4-6 7-6(2) 6-2 to set up a second round tie with Gilles Muller.  Dimitrov looked to be heading out of the tournament after a sloppy start to his first rounder.  Mathieu…