After merge fixes of test result.

Bug#10568 - Function 'LAST_DAY(date)' does not return NULL for invalid argument.
Manual merge.

Wrong comparing method were choosen which results in false comparison.

Make Item_bool_func2::fix_length_and_dec() to get type and field from
real_item() to make REF_ITEM pass the check. 

Moved the key statistics update to info().
The table is not locked in open(). This made wrong stats possible.

No test case for the test suite.
This happens only with heavy concurrency.
A test script is added to the bug report.

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

  Correction after manula merge.

into sanja.is.com.ua:/home/bell/mysql/bk/work-bug3-5.0

into mysql.com:/home/timka/mysql/src/5.0-virgin

into sanja.is.com.ua:/home/bell/mysql/bk/work-bug3-5.0

into mysql.com:/home/timka/mysql/src/5.0-virgin

into mysql.com:/home/timka/mysql/src/4.1-virgin

into sanja.is.com.ua:/home/bell/mysql/bk/work-bug3-5.0

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

into mysql.com:/home/svoj/devel/mysql/mysql-5.0.9

into mysql.com:/opt/local/work/mysql-5.0-sp_instr

into mysql.com:/home/psergey/mysql-5.0-bug8441

into mysql.com:/home/psergey/mysql-5.0-bug8441

into mysql.com:/home/timka/mysql/src/4.1-virgin

into mysql.com:/Users/kent/mysql/bk/mysql-4.1

into rurik.mysql.com:/home/igor/dev/mysql-4.1-1

into mysql.com:/home/psergey/mysql-4.1-bug10151

  Fix for fix for bug #9728
  Error caused server hang on prepared insert ... select

Fix for compilation failure with Forte Developer C++.

into mysql.com:/opt/local/work/mysql-5.0-sp_instr

  We need every instruction to have its own arena, because we want to
  track instruction's state (INITIALIZED_FOR_SP -> EXECUTED). Because of 
  `if' statements and other conditional instructions used in stored 
  procedures, not every instruction of a stored procedure gets executed 
  during the first (or even subsequent) execution of the procedure. 
  So it's better if we track the execution state of every instruction 
  independently.
  All instructions of a given procedure now also share sp_head's 
  mem_root, but keep their own free_list.
  This simplifies juggling with free Item lists in sp_head::execute.
- free_items() moved to be a member of Query_arena. 
- logic of 'backup_arena' debug member of Query_arena has been
  changed to support
  multi-backups. Until now, TRUE 'backup_arena' meant that there is
  exactly one active backup of the THD arena. Now it means simply that
  the arena is used for backup, so that we can't accidentally overwrite an 
  existing backup. This allows doing multiple backups, e.g. in
  sp_head::execute and Cursor::fetch, when THD arena is already backed up
  but we want to set yet another arena (usually the 'permanent' arena,
  to save permanent transformations/optimizations of a parsed tree).

into mysql.com:/Users/kent/mysql/bk/mysql-5.0

into mysql.com:/Users/kent/mysql/bk/mysql-5.0-release

  Might need a restart after test with special TZ
  Removed unused argument to run_mysqltest()

into sanja.is.com.ua:/home/bell/mysql/bk/work-bug3-5.0