EXPLAIN EXTENDED warning.

Query optimizer searches for the constant tables and optimizes them away. This
means that fields of such tables are substituted for their values and on later
phases they are treated as constants. After this constant tables are removed
from the query execution plan. Nevertheless constant tables were shown in 
the EXPLAIN EXTENDED warning thus producing query that might be not an
equivalent of the original query.
        
Now the print_join function skips all tables that were optimized away from
printing to the EXPLAIN EXTENDED warning. If all tables were optimized away it
produces the 'FROM dual' clause.

Fix a regression that crept in when downporting Windows improvements.
Instead of a shutdown thread, another thread that  handledsocket connection was created.

Ensure full path to dtrace binary is used, fixes builds where
/usr/sbin is not in $PATH.

Bug #33629: last_day function can return null, but has 'not null' flag set for result

LAST_DAY and MAKEDATE functions are documented as
returning NULL value, but actually they was implemented
as returning NOT NULL typed values.

That caused a confusing error "ERROR 1048 (23000): Column
'...' cannot be null" on queries like: 

  SELECT 1 FROM (SELECT LAST_DAY('0')) a;

indexed column in mysql.plugin table should use case-insensitive collation
for index lookups to work

(backport from 6.0)

Original revision in 6.0:
------------------------------------------------------------
revno: 2599.108.1
committer: Alexander Nozdrin <alik@sun.com>
branch nick: 6.0-rpl-bug40128
timestamp: Wed 2009-01-21 15:33:42 +0300
message:
  Fix for Bug#40128: drop-no_root fails under windows in 6.0-rpl.
  
  The problem was that directories with no permission (000) files
  are deleted differently on UNIX and on Windows.
  
  On UNIX, 000-permission file is deleted perfectly, but other files
  are left in the directory.
  
  On Windows, 000-permission file is not deleted, but other files
  are deleted.
  
  Also, the fix needed a change in mysqltest.c: 'chmod' directive
  should return a positive error code (in order to be handled).
  It's decided to return a constant '1' for all error codes
  just to be OS-independent.
------------------------------------------------------------

Original revision in mysql-6.0-codebase is:

revno: 2617.31.14
committer: Konstantin Osipov <kostja@sun.com>
branch nick: mysql-6.0-runtime
timestamp: Sat 2009-03-28 11:42:55 +0300
message:
  Bug#35297 SHOW CREATE EVENT does not show the DEFINER:
  update test result after a merge from now.

Original revision is from mysql-6.0-codebase:

revno: 2617.23.13
committer: Alexander Nozdrin <alik@sun.com>
branch nick: 6.0-rt-bug34828
timestamp: Tue 2009-02-24 14:25:46 +0300
message:
  A patch for Bug#34828: OF is taken as OFF and a value of 0
  is set for variable SQL_notes.
  
  The problem was that partial match was allowed for keywords.
  
  A fix is to disable partial match and require full match.

Original revision is from mysql-6.0-codebase:

revno: 2630.3.1
committer: Alexander Nozdrin <alik@mysql.com>
branch nick: 6.0-rt-bug26704
timestamp: Thu 2008-05-29 21:04:06 +0400
message:
  A fix for Bug#26704: Failing DROP DATABASE brings
  mysql-client out of sync.

  The problem was that we changed current database w/o caring
  whether it was dropped successfully or not.

  The fix is not to change current database if we failed to drop it.

Backport of the fix for BUG#33730 "Full table scan instead selected partitions for query more than 10 partitions"
from 6.0, made in sergefp@mysql.com-20090205190644-q8632sniogedhtsu

(from revision konstantin@mysql.com-20080627154042-923m6lzk7z77lrgj ). This moves the slow part
(10 seconds over 13) into a separate big test.