Fix definition of bool_lt in the linearisation library
Fix definition of bool_lt in the linearisation library

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