(1) fix type error

(2) remove empty "--error ER_PARSE_ERROR"
(3) change three members in class select_unit to protected.

mysql-test/main/except.test

@@ -66,7 +66,6 @@ select 1 as a from dual except select 1 from dual;
 select 1 from dual ORDER BY 1 except select 1 from dual;
 
 select 1 as a from dual union all select 1 from dual;
---error ER_PARSE_ERROR
 
 
 create table t1 (a int, b blob, a1 int, b1 blob) engine=MyISAM;

mysql-test/main/intersect.test

@@ -65,7 +65,6 @@ select 1 as a from dual intersect select 1 from dual;
 select 1 from dual ORDER BY 1 intersect select 1 from dual;
 
 select 1 as a from dual union all select 1 from dual;
---error ER_PARSE_ERROR
 
 
 

sql/sql_class.h

@@ -5708,7 +5708,7 @@ class TMP_TABLE_PARAM :public Sql_alloc
 
 class select_unit :public select_result_interceptor
 {
-public:
+protected:
   uint curr_step, prev_step, curr_sel;
   enum sub_select_type step;
 public:
@@ -5870,7 +5870,7 @@ class select_unit_ext :public select_unit
   };
   int send_data(List<Item> &items);
   void change_select();
-  int unfold_record(int cnt);
+  int unfold_record(longlong cnt);
   bool send_eof();
   bool force_enable_index_if_needed()
   {

sql/sql_union.cc

@@ -499,7 +499,7 @@ bool select_unit_ext::disable_index_if_needed(SELECT_LEX *curr_sl)
     -1  conversion happened
 */
 
-int select_unit_ext::unfold_record(int cnt)
+int select_unit_ext::unfold_record(longlong cnt)
 {
 
   DBUG_ASSERT(cnt > 0);