It turns out that this test case no longer fails with the discrepancy
  in numbers that was the original cause for disabling this test (and showed
  potential genuine issues with the query cache). Therefore
  this test is being enabled after some minor adjustment of error codes and
  messages.

Details:
1. Add missing "disconnect <session>"
2. Take care that the disconnects are finished when the test terminates
3. Replace error names by error numbers
4. Minor beautifying of script code

 
Field_time::get_time() did not initialize some members of 
MYSQL_TIME which led to valgrind warnings when those members 
were accessed in Protocol_simple::store_time(). 
 
It is unlikely that this bug could result in wrong data 
being returned, since Field_time::get_time() initializes the 
'day' member of MYSQL_TIME to 0, so the value of 'day' 
in Protocol_simple::store_time() would be 0 regardless 
of the values for 'year' and 'month'.

mysql-test/r/type_time.result:
  Added a test case for bug #44792.
mysql-test/t/type_time.test:
  Added a test case for bug #44792.
sql/field.cc:
  Field_time::get_time() did not initialize some members of 
  MYSQL_TIME which led to valgrind warnings when those members 
  were accessed in Protocol_simple::store_time().

Remove a cast (which shouldn't have got here anyway)
which might lose significant bits beyond 4 GB RAM.


mysys/safemalloc.c:
  Vlad's comment to the cast:
    pointless cast from size_t to uint that loses
    significant bits, when safe_malloc allocates more than 4GB Ram.
    safemalloc is not used in release binaries,
    so it is not absolutely critical.
  
  It got into the sources by a wrong merge resolution.

In UNION if we use last SELECT without braces and this
SELECT have ORDER BY clause, such clause belongs to
global UNION. It is parsed like last SELECT
part and used further as 'unit->global_parameters->order_list' value.
During DESCRIBE EXTENDED we call select_lex->print_order() for
last SELECT where order fields refer to tmp table 
which already freed. It leads to crash.
The fix is clean up global_parameters->order_list
instead of fake_select_lex->order_list.


mysql-test/r/union.result:
  test result
mysql-test/t/union.test:
  test case
sql/sql_union.cc:
  In UNION if we use last SELECT without braces and this
  SELECT have ORDER BY clause, such clause belongs to
  global UNION. It is parsed like last SELECT
  part and used further as 'unit->global_parameters->order_list' value.
  During DESCRIBE EXTENDED we call select_lex->print_order() for
  last SELECT where order fields refer to tmp table 
  which already freed. It leads to crash.
  The fix is clean up global_parameters->order_list
  instead of fake_select_lex->order_list.

  UNIX sockets need to be on a path shorter than 70 characters on some older platofrms.
  MTRv1 tries to fix this by moving the socket to the $TMPDIR, however this causes
  issues with certain tests on Windows.

  Fixed by not applying any hacks on Windows - Windows does not need them.

It is not possible to prevent the server from starting if a mandatory
built-in plugin fails to start. This can in some cases lead to data
corruption when the old table name space suddenly is used by a different
storage engine.

A boolean command line option in the form of --foobar is automatically
created for every existing plugin "foobar". By changing this command line
option from a boolean to a tristate { OFF, ON, FORCE } it is possible to
specify the plugin loading policy for each plugin.

The behavior is specified as follows:
   OFF   = Disable the plugin and start the server
   ON    = Enable the plugin and start the server even if an error occurrs
           during plugin initialization.
   FORCE = Enable the plugin but don't start the server if an error occurrs
           during plugin initialization.


mysql-test/lib/mtr_cases.pm:
  * Changed --<pluginname> from a boolean to a tristate.
mysys/my_getopt.c:
  * Changed --<pluginname> from boolean to tristate. Optional arguments
    must still work for tristates. It is praxis that disable means value 0
    and enable is value 1. Since plugin name is the only tristate with
    optional arguments this principle will still hold.
sql/sql_plugin.cc:
  * Changed --<pluginname> option from a boolean type to a tristate.
    - FORCE will now terminate the server if the plugin fails to
      initialize properly.
  * Refactored prototypes for test_plugin_options() and construct_options()
    to get rid of the 'enable' value pointer.
  * Cleaned up code related to option name constructing.
  * Added documentation
sql/sql_plugin.h:
  * Introduced new member to st_plugin_int structure.

UNIX sockets need to be on a path shorter than 70 characters on some older platofrms.
MTRv1 tries to fix this by moving the socket to the $TMPDIR, however this causes
issues with certain tests on Windows.

Fixed by not applying any hacks on Windows - Windows does not need them.

checking in a test case that will reproduce
the error on v5r4.

mysql-test/suite/ibmdb2i/include/have_i54.inc:
  Bug#44232 Error msg should be improved when collation not supported.
mysql-test/suite/ibmdb2i/r/ibmdb2i_bug_44232.result:
  Bug#44232 Error msg should be improved when collation not supported.
mysql-test/suite/ibmdb2i/t/ibmdb2i_bug_44232.test:
  Bug#44232 Error msg should be improved when collation not supported.

This patch fixes compilation warning, "conversion from 'time_t' to 'ulong', 
possible loss of data". 
The fix is to typecast time_t to ulong before assigning it to ulong. 
Backported this from 6.0-bugteam tree.


storage/archive/ha_archive.cc:
  type casting time_t to ulong before assigning.
storage/federated/ha_federated.cc:
  type casting time_t to ulong before assigning.
storage/innobase/handler/ha_innodb.cc:
  type casting time_t to ulong before assigning.
storage/myisam/ha_myisam.cc:
  type casting time_t to ulong before assigning.

            SQL_SELECT::test_quick_select

The crash was caused by an incomplete cleanup of JOIN_TAB::select
during the filesort of rows for GROUP BY clause inside a subquery.
Queries where a quick index access is replaced with filesort was
was affected. For example:

  SELECT 1 FROM
    (SELECT COUNT(DISTINCT c1) FROM t1
       WHERE c2 IN (1, 1) AND c3 = 2 GROUP BY c2) x

Quick index access related data in the SQL_SELECT::test_quick_select
function was inconsistent after an incomplete cleanup.
This function has been completed to prevent crashes in the
SQL_SELECT::test_quick_select function.


mysql-test/include/mix1.inc:
  Add test case for bug #44290.
mysql-test/r/innodb_mysql.result:
  Add test case for bug #44290.
sql/sql_select.cc:
  Bug #44290: explain crashes for subquery with distinct in
              SQL_SELECT::test_quick_select
  
  Quick index access related data in the SQL_SELECT::test_quick_select
  function was inconsistent after an incomplete cleanup.
  This function has been completed to prevent crashes in the
  SQL_SELECT::test_quick_select function.