Implement set difference and symmetric difference builtins
Implement set difference and symmetric difference builtins

jjdekker/libminizinc,tias/libminizinc,nathanielbaxter/libminizinc,jjdekker/libminizinc,tias/libminizinc,nathanielbaxter/libminizinc,jjdekker/libminizinc,jjdekker/libminizinc,nathanielbaxter/libminizinc,nathanielbaxter/libminizinc