TRANSACTION ROLLBACK

Description:  During the rollback operation, a blob page 
is removed earlier than desired.  Consider following scenario:

1. create table t1(a int primary key,b blob) engine=innodb;
2. insert into t1 values (1,repeat('b',9000));
3. begin;
4. update t1 set b=concat(b,'b');
5. update t1 set a=a+1;
6. insert into t1 values (1,repeat('b',9000));
7. rollback;

The update operation in line 5 produces 2 undo log record. The first
undo record (TRX_UNDO_DEL_MARK_REC) goes to trx->update_undo and the
second undo record (TRX_UNDO_INSERT_REC) goes to trx->insert_undo.
During rollback, they are executed out of order.

When the undo record TRX_UNDO_DEL_MARK_REC is applied/executed,
the blob ownership is also reset.  Because of this the blob page
is released earlier than desired.  This blob page must have been
freed only as part of applying/executing the undo record
TRX_UNDO_INSERT_REC.

This problem can be avoided by executing the undo records in
order.  This patch will make innodb to execute the undo records
in order.

rb://1125 approved by Marko.