Fix forward decl for #46 Passing tests on linux
Fix forward decl for #46
Passing tests on linux

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