Stored procedure execution sometimes placed the address of auto variables
in the list of Item changes to undo in THD::rollback_item_tree_changes().
This could cause stack corruption.

mysql-test-run now fails in case of warnings

into  mysql.com:/home/my/mysql-5.0

into  mysql.com:/home/my/mysql-5.0

into  mysql.com:/home/my/mysql-5.0

into  mysql.com:/home/my/mysql-5.0

into  ua141d10.elisa.omakaista.fi:/home/my/bk/mysql-5.0

is only to make sure that this will not be fixed, as it is
intended behaviour. Documentation will be improved accordingly.

into  mysql.com:/home/my/mysql-5.0

This caused sp-vars.test to fail

into  rurik.mysql.com:/home/igor/dev/mysql-5.0-0

into mysql.com:/home/hf/work/mysql-5.0.mrg

into mysql.com:/home/hf/work/mysql-5.0.mrg

into  rurik.mysql.com:/home/igor/dev/mysql-5.0-0

into  production.mysql.com:/usersnfs/svojtovich/mysql-5.0

into mysql.com:/home/hf/work/mysql-5.0.mrg

into  mysql.com:/space/pekka/ndb/version/my50

into  mysql.com:/home/alexi/innodb/mysql-5.0-ss521

 Fixed BUG#19366: "consistent_snapshot.test fails".

into mysql.com:/home/hf/work/mysql-4.1.mrg

into  mysql.com:/home/alexi/innodb/mysql-4.1-ss26

into  mysql.com:/home/alexi/innodb/mysql-5.0-ss521-work
 Null-merge.

 Fixed BUG#19366: "consistent_snapshot.test fails".

into mysql.com:/home/hf/work/mysql-4.1.mrg

into mysql.com:/home/hf/work/mysql-5.0.mrg

into  april.(none):/home/svoj/devel/mysql/BUG17810/mysql-5.0

into  april.(none):/home/svoj/devel/mysql/BUG17810/mysql-5.0

into mysql.com:/home/hf/work/mysql-4.1.mrg

into mysql.com:/home/hf/work/mysql-4.1.mrg

into mysql.com:/home/hf/work/mysql-4.1.mrg

This performance degradation was due to the fact that some
cost evaluation code added into 4.1 in the function find_best was
not merged into the code of the function best_access_path added
together with other code for greedy optimizer.
Added a parameter to the function print_plan. The parameter contains
accumulated cost for a given partial join.
 
The patch does not include a special test case since this performance
degradation is hard to reproduse with a simple example.

TODO: make the function find_best use the function best_access_path
in order to remove duplication of code which might result in incomplete
merges in the future.