Fix simplification of linear constraints to variable bounds (could be incorrect with negative coefficients)
Fix simplification of linear constraints to variable bounds (could be incorrect with negative coefficients)

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