Bug #2959 UTF8 charset breaks joins with mixed column/string constant

Description:
When using utf8 charset (with both _ci and _bin collations) joins with a mix of column and string constant join criteria fail.

How to repeat:
CREATE TABLE test ( a varchar(10) ) CHARACTER SET utf8;
INSERT INTO test VALUES ( 'test' );
SELECT a.a, b.a FROM test a, test b WHERE a.a = b.a;
SELECT a.a, b.a FROM test a, test b WHERE a.a = 'test' and b.a = 'test';
SELECT a.a, b.a FROM test a, test b WHERE a.a = b.a and a.a = 'test';
DROP TABLE test;

Suggested fix:
n/a

I have another test case which might be relevant to this bug:

create table x (a char(255));
insert into x values('b');

select * from x where a = 'b';
+------+
| a |
+------+
| b |
| b |
+------+
2 rows in set (0.00 sec)

select * from x where a = 'b' and a = 'b';

Empty set (0.00 sec)

mysql> select * from x where a = 'b' and a != 'b';
+------+
| a |
+------+
| b |
+------+

Hoewer I get same results even after changing table default character set to latin1 as well as NAMES and alos differrent combinations of both.

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