Fix error in use of bound for minpoly over Z.
Fix error in use of bound for minpoly over Z.

jpflori/flint2,fredrik-johansson/flint2,jpflori/flint2,fredrik-johansson/flint2,wbhart/flint2,fredrik-johansson/flint2,dsroche/flint2,dsroche/flint2,wbhart/flint2,jpflori/flint2,wbhart/flint2,dsroche/flint2,jpflori/flint2,dsroche/flint2