Add static cast functions that can be called on NULL pointers
Add static cast functions that can be called on NULL pointers

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