POLY: improve doxygen comments

src/poly.c

@@ -152,6 +152,9 @@ void poly_delete_all(fmpz_poly_t *poly, ...)
  * so we don't have to deal with the intermediate
  * nmod_poly_t type if we don't need it.
  *
+ * This also normalises the coefficients to the interval
+ * 0 <= r < m.
+ *
  * @param a the polynom to apply the modulus to
  * @param mod the modulus
  */
@@ -174,6 +177,9 @@ void fmpz_poly_mod_unsigned(fmpz_poly_t a,
  * so we don't have to deal with the intermediate
  * nmod_poly_t type if we don't need it.
  *
+ * This also normalises the coefficients to the interval
+ * -m/2 <= r < m/2.
+ *
  * @param a the polynom to apply the modulus to
  * @param mod the modulus
  */