Some fixes to builtins
Some fixes to builtins

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