Mysql IF_IDLE patch

I isolated Google’s IF_IDLE feature from SqlChanges; part of the Google V2 patch.
I diffed this IF_IDLE patch for mysql-5.0.68-percona-highperf but it’ll patch mysql-5.0.67 as well.

This simple and brilliant change allows us to
attempt to kill idle mysql processes while avoiding race conditions.

KILL IF_IDLE <id>

mysql> SHOW PROCESSLIST;
+----+-------------+-----------+-----------+---------+------+----------------------------------+
| Id | User        | Host      | db        | Command | Time | State                            | Info
+----+-------------+-----------+-----------+---------+------+----------------------------------+
|  2 | system user |           | NULL      | Connect | 2192 | Waiting for master to send event | NULL
| 13 | root        | localhost | NULL      | Query   |    0 | NULL                             | show processlist
| 30 | root        | localhost | NULL      | Sleep   |    2 |                                  | NULL
+----+-------------+-----------+-----------+---------+------+----------------------------------+
4 rows in set (0.00 sec)
mysql> KILL IF_IDLE 30;
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW PROCESSLIST;
+----+-------------+-----------+-----------+---------+------+----------------------------------+
| Id | User        | Host      | db        | Command | Time | State                            | Info
+----+-------------+-----------+-----------+---------+------+----------------------------------+
|  2 | system user |           | NULL      | Connect | 2357 | Waiting for master to send event | NULL
| 13 | root        | localhost | NULL      | Query   |    0 | NULL                             | show processlist
+----+-------------+-----------+-----------+---------+------+----------------------------------+
3 rows in set (0.00 sec)