Fix another compiler warning on Windows in InnoDB.

storage/innobase/handler/ha_innodb.cc:
  Fix compiler warning: ::get_auto_increment takes a ulonglong
  for nb_desired_values, but InnoDB's trx struct stores it as
  a ulint (unsigned long).  Probably harmless, as a single
  statement won't be asking for more than 2^32 rows.

storage/innobase/handler/ha_innodb.cc

@@ -7324,7 +7324,7 @@ ha_innobase::get_auto_increment(
 		/* Called for the first time ? */
 		if (prebuilt->trx->n_autoinc_rows == 0) {
 
-			prebuilt->trx->n_autoinc_rows = nb_desired_values;
+			prebuilt->trx->n_autoinc_rows = (ulint) nb_desired_values;
 
 			/* It's possible for nb_desired_values to be 0:
 			e.g., INSERT INTO T1(C) SELECT C FROM T2; */