Bug #17 Incorrect parsing of UNION in IN subselect

Description:
UNION subselects with braces inside is incorrectly parsed. 

How to repeat:
mysql> (select 1) union (select 2) limit 2; 
+---+ 
| 1 | 
+---+ 
| 1 | 
| 2 | 
+---+ 
2 rows in set (0.00 sec) 
it is OK 
 
mysql> select 1 in (select 1 union select 2); 
+--------------------------------+ 
| 1 in (select 1 union select 2) | 
+--------------------------------+ 
|                              1 | 
+--------------------------------+ 
1 row in set (0.00 sec) 
 
it is OK, too 
 
 
mysql> select 1 in ((select 1) union (select 2) limit 2); 
ERROR 1064: You have an error in your SQL syntax.  Check the manual that 
corresponds to your MySQL server version for the right syntax to use near 'union (select 
2) limit 2)' at line 1 
 
it should not be syntax error, but "This version of MySQL doesn't yet support 'LIMIT & 
IN/ALL/ANY/SOME subquery'" 
 
ysql> select 1 in ((select 1) union (select 2)); 
ERROR 1064: You have an error in your SQL syntax.  Check the manual that 
corresponds to your MySQL server version for the right syntax to use near 'union (select 
2))' at line 1 
 
it should be performed 
 

Suggested fix:
Sorry, If I whold have suggestion about fix I had fixed it already.

This bug happens to due to error in parsing.

A problem is caused by parenthesis parsing in 4.1.

Simply, with:
select 1 in ((select 1) union (select 2));

first select in UNION drops in select_init2 instead in
select_init1 parser label !!!

the problem is that "SELECT 1" is a correct expression.
E.g. this query works:

SELECT 1 IN ((SELECT 1),(SELECT 2));

I cannot see how to fix parser to distinguish

SELECT 1 IN ((SELECT 1) UNION (SELECT 2))

from the above with only one look-ahead. At least not without very ugly workarounds and really lousy grammar.

This bug will go away automatically, when we'll get new parser (not bison-based)