on server shutdown after SELECT with CONVERT_TZ

It's wrong to return my_empty_string from val_str().
Removing my_empty_string. Using make_empty_result() instead.

Assertion `mon > 0 && mon < 13' failed.'

MDEV-5337: Wrong result in mariadb 5.5.32 with ORDER BY + LIMIT when 
index_condition_pushdown=on
- in test_if_skip_sort_order(), correct the condition under which
  we have the code that restores the previously pushed index condition.

The crash happened because Item_func_monthname was derived from
Item_func_month, so Item_func_monthname::is_null() did not work fine.
Backporting a change from 5.5: Item_func_monthname is now derived from
Item_str_func.

- convert_subq_to_sj() must connect child select's tables into 
  parent select's TABLE_LIST::next_local chain.  
- The problem was that it took child's leaf_tables.head() which
  is different. This could cause certain tables (in this bug's case,
  child select's non-merged semi-join) not to be present in 
  TABLE_LIST::next_local chain.  Which would cause non-merged semi-join
  not to be initialized in setup_tables(), which would lead to 
  NULL pointer dereference.

THD::thd->activate_stmt_arena_if_needed() should be used to temporary activating statement arena instead of direct usage of THD::set_n_backup_active_arena() because possible such scenario:
  1) func1 saves current arena and activates copy1 of statement arena
  2) func2 saves copy1 of statement arena setup by func1 and activates copy2
  3) some changes made for copy 2
  4) func2 stores changed copy2 back to statenet arena and activates copy1
  5) func1 store unchanged copy1 back to statemnt arena (rewrite changed copy 2 so changes become lost) and activates arena which was before.

THD::thd->activate_stmt_arena_if_needed() should be used to temporary activating statement arena instead of direct usage of THD::set_n_backup_active_arena() because possible such scenario:
  1) func1 saves current arena and activates copy1 of statement arena
  2) func2 saves copy1 of statement arena setup by func1 and activates copy2
  3) some changes made for copy 2
  4) func2 stores changed copy2 back to statenet arena and activates copy1
  5) func1 store unchanged copy1 back to statemnt arena (rewrite changed copy 2 so changes become lost) and activates arena which was before.

update_used_tables() should be called after handling derived tables in any case.

Materialization forced in case if rand() used in view or derived table to avoud several calls of rand for gting value of a field.

Fixed set variable uncachable flag from - it shouldbe a side effect not a random value.

The fix for bug #27937 was incomplete: it did not handle correctly the queries
containing UNION with global ORDER BY in subselects.

a memory leak in save_index() first seen in the test case for mdev-5382.

When marking used columns the function find_field_in_table_ref() erroneously
called the walk method for the real item behind a view/derived table field
with the second parameter set to TRUE.
This erroneous code was introduced in 2006. 

Correct processing of view/derived with no tables added.

"Conditional jump or move depends on uninitialised"
in Item_time_typecast::get_date.

Adding "null_value" into the debug assert condition.

modified:
  mysql-test/r/func_time.result
  mysql-test/t/func_time.test
  sql-common/my_time.c
  sql/item_func.h
  sql/item_timefunc.cc
  sql/mysql_priv.h
  sql/time.cc

Fix ha_myisammrg::update_create_info() to do what ha_myisammrg::append_create_info() does -
take sub-table names from TABLE_LIST, not reverse engineer tablefile names.

Backport praveenkumar.hulakund@oracle.com-20120127081643-u7dxy23i8yyqarm7 from mysql-5.6

- For INSERT ... SELECT ... ON DUPLICATE KEY UPDATE, table elimination should 
  check which tables are referenced in the ON DUPLICATE KEY UPDATE clause.

remove_eq_conds() in the function make_join_statistics().

The earlier pushed fix for the bug was incomplete. It did not remove
the main cause of the problem: the function remove_eq_conds()
removed always true multiple equalities from any conjunct, but did not
adjust the list of them stored in Item_cond_and::cond_equal.current_level.

Simplified the test case for the bug and moved it to another test file.

The fix triggered changes in EXPLAIN EXTENDED for some queries. 

Fixed.

This bug was a consequence of the incorrect fix for bug mdev-5091.

mysql_tzinfo_to_sql is not compiled under Windows in the pre-5.5 versions.
Do not set the MYSQL_TZINFO_TO_SQL variable in the version prior to 5.5
under Windows.

The function SELECT_LEX::update_used_tables should process all
ORDER BY lists in any subselect of a union.