Updated ecm_add, now handles corner cases (Either of points is 0, points are same).
Updated ecm_add, now handles corner cases (Either of points is 0, points are same).

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