Fix for the bug #2976: NATURAL JOIN produces duplicate columns.

Improvement natural join code in the setup_conds().

mysql-test/r/join.result

@@ -277,11 +277,11 @@ CREATE TABLE t2 (ID INTEGER NOT NULL PRIMARY KEY, Value2 VARCHAR(255));
 INSERT INTO t1 VALUES (1, 'A');
 INSERT INTO t2 VALUES (1, 'B');
 SELECT * FROM t1 NATURAL JOIN t2 WHERE 1 AND (Value1 = 'A' AND Value2 <> 'B');
-ID	Value1	ID	Value2
+ID	Value1	Value2
 SELECT * FROM t1 NATURAL JOIN t2 WHERE 1 AND Value1 = 'A' AND Value2 <> 'B';
-ID	Value1	ID	Value2
+ID	Value1	Value2
 SELECT * FROM t1 NATURAL JOIN t2 WHERE (Value1 = 'A' AND Value2 <> 'B') AND 1;
-ID	Value1	ID	Value2
+ID	Value1	Value2
 drop table t1,t2;
 create table t1 (i int);
 create table t2 (i int);

mysql-test/r/join_outer.result

@@ -124,8 +124,8 @@ grp	a	c	id	a	c	d
 3	5	C	3	5	B	5
 3	6	D	3	6	C	6
 select t1.*,t2.* from t1 natural join t2;
-grp	a	c	id	a	c	d
-1	1	a	1	1	a	1
+grp	a	c	id	d
+1	1	a	1	1
 drop table t1,t2;
 CREATE TABLE t1 (
 usr_id INT unsigned NOT NULL,
@@ -467,10 +467,10 @@ count	color
 15	white
 7	green
 select * from t2 natural join t1;
-count	color	color	name
-10	green	green	lime
-7	green	green	lime
-5	black	black	grape
+count	color	name
+10	green	lime
+7	green	lime
+5	black	grape
 select t2.count, t1.name from t2 natural join t1;
 count	name
 10	lime

mysql-test/r/select.result

@@ -2279,10 +2279,10 @@ a	a	a
 2	2	2
 3	3	3
 select * from t1 natural join (t1 as t2 left join t1 as t3 using (a));
-a	a	a
-1	1	1
-2	2	2
-3	3	3
+a	a
+1	1
+2	2
+3	3
 select * from (t1 as t2 left join t1 as t3 using (a)) natural join t1;
 a	a	a
 1	1	1