Fix unary minus operator to create type correct code
Fix unary minus operator to create type correct code

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