added virtual destructor to PolymorphicCaster
added virtual destructor to PolymorphicCaster

adasworks/cereal,USCiLab/cereal,jkhoogland/cereal,USCiLab/cereal,abutcher-gh/cereal,fawkes74/cereal,fawkes74/cereal,adasworks/cereal,jkhoogland/cereal,abutcher-gh/cereal