added XML to all tests in unittests
added XML to all tests in unittests

Some things are failing, will need to look at this later.

string test is commented out for XML since it doesn't work with wchar yet
priority_queue test is commented out for XML since it doesn't work with empty structs automatically

USCiLab/cereal,jonathan-beard/cereal,syxolk/cereal,sschaetz/cereal,vcatechnology/cereal,jkhoogland/cereal,abutcher-gh/cereal,guker/cereal,adasworks/cereal,JosephLaurino/cereal,stevehickman/cereal,RobertoMalatesta/cereal,sschaetz/cereal,jonathan-beard/cereal,arvidsson/cereal,syxolk/cereal,adasworks/cereal,heamon7/cereal,USCiLab/cereal,lyager/cereal,guker/cereal,vcatechnology/cereal,fawkes74/cereal,headupinclouds/cereal,heamon7/cereal,arvidsson/cereal,fawkes74/cereal,jkhoogland/cereal,headupinclouds/cereal,JosephLaurino/cereal,stevehickman/cereal,RobertoMalatesta/cereal,abutcher-gh/cereal,lyager/cereal