Due to this bug in the function generate_derived_keys_for_table some
key definitions to access materialized derived tables or materialized
views were constructed with invalid info for their key parts.
This could make the server crash when it optimized queries using 
materialized derived tables or materialized views. 

This crashing bug could manifest itself at execution of join queries
over materialized derived tables with IN subquery predicates in the
where clause. If for such a query the optimizer chose to use duplicate
weed-out with duplicates in a materialized derived table and chose to
employ join cache the the execution could cause a crash of the server.
It happened because the JOIN_CACHE::init method assumed  that the value
of TABLE::file::ref is set at the moment when the method was called 
for the employed join cache. It's true for regular tables, but it's 
not true for materialized derived tables that are filled now at the
first access to them, i.e. after the JOIN_CACHE::init has done its job.

To fix this problem for any ROWID field of materialized derived table
the procedure that copies fields from record buffers into the employed
join buffer first checks whether the value of TABLE::file::ref has 
been set for the table, and if it's not so the procedure sets this value.

  
Analysis:
  The failed assert ensured that the choice of subquery strategy
  is performed only for queries with at least one table. If there
  is a LIMIT 0 clause all tables are removed, and the subquery is
  neither optimized, nor executed during actual optimization. However,
  if the query is EXPLAIN-ed, the EXPLAIN execution path doesn't remove
  the query tables if there is a LIMIT 0 clause. As a result, the
  subquery optimization code is called, which violates the ASSERT
  condition.
  
Solution:
  Transform the assert into a condition, and if the outer query
  has no tables assume that there will be at most one subquery
  execution.
  
  There is potentially a better solution by reengineering the
  EXPLAIN/optimize code, so that subquery optimization is not
  done if not needed. Such a solution would be a lot bigger and
  more complex than a bug fix.

BUG#751484: Valgrind warning / sporadic crash in evaluate_join_record sql_select.cc:14099 with semijoin
- Added testcase. The bug is most likely fixed by MWL#90 code.

The function create_view_field in some cases incorrectly set the maybe_null
flag for the returned items.

Added mytop to distribution (with some small trivial changes to make it workg good also for MariaDB)

scripts/CMakeLists.txt:
  Added mytop
scripts/Makefile.am:
  Added mytop
scripts/make_binary_distribution.sh:
  Added mytop
scripts/make_win_bin_dist:
  Added mytop
scripts/mytop.sh:
  Added mytop (with some small trivial changes to make it workg good also for MariaDB)
support-files/mysql.spec.sh:
  Added mytop

Split status variable Rows_read to Rows_read and Rows_tmp_read so that one can see how much real data is read.
Same was done with with Handler_update and Handler_write.
Fixed bug in MEMORY tables where some variables was counted twice.
Added new internal handler call 'ha_close()' to have one place to gather statistics.
Fixed bug where thd->open_options was set to wrong value when doing admin_recreate_table()


mysql-test/r/status.result:
  Updated test results and added new tests
mysql-test/r/status_user.result:
  Udated test results
mysql-test/t/status.test:
  Added new test for temporary table status variables
sql/ha_partition.cc:
  Changed to call ha_close() instead of close()
sql/handler.cc:
  Added internal_tmp_table variable for easy checking of temporary tables.
  Added new internal handler call 'ha_close()' to have one place to gather statistics.
  Gather statistics for internal temporary tables.
sql/handler.h:
  Added handler variables internal_tmp_table, rows_tmp_read.
  Split function update_index_statistics() to two.
  Added ha_update_tmp_row() for faster tmp table handling with more statistics.
sql/item_sum.cc:
  ha_write_row() -> ha_write_tmp_row()
sql/multi_range_read.cc:
  close() -> ha_close()
sql/mysqld.cc:
  New status variables: Rows_tmp_read, Handler_tmp_update and Handler_tmp_write
sql/opt_range.cc:
  close() -> ha_close()
sql/sql_base.cc:
  close() -> ha_close()
sql/sql_class.cc:
  Added handling of rows_tmp_read
sql/sql_class.h:
  Added new satistics variables.
  rows_read++  ->  update_rows_read() to be able to correctly count reads to internal temp tables.
  Added handler::ha_update_tmp_row()
sql/sql_connect.cc:
  Added comment
sql/sql_expression_cache.cc:
  ha_write_row() -> ha_write_tmp_row()
sql/sql_select.cc:
  close() -> ha_close()
  ha_update_row() -> ha_update_tmp_row()
sql/sql_show.cc:
  ha_write_row() -> ha_write_tmp_row()
sql/sql_table.cc:
  Fixed bug where thd->open_options was set to wrong value when doing admin_recreate_table()
sql/sql_union.cc:
  ha_write_row() -> ha_write_tmp_row()
sql/sql_update.cc:
  ha_write_row() -> ha_write_tmp_row()
sql/table.cc:
  close() -> ha_close()
storage/heap/ha_heap.cc:
  Removed double counting of statistic variables.
  close -> ha_close() to get tmp table statistics.
storage/maria/ha_maria.cc:
  close -> ha_close() to get tmp table statistics.

Ensured valid calculations of the estimates stored in JOIN_TAB::used_fieldlength.

Made mergeable views and mergeable derived tables transparent for
the MIN/MAX optimization.

fixed by the patch for LP bug 798621.

The following were missing in the patch for mwl106:
- KEY_PART_INFO::fieldnr were not set for generated keys to access
  tmp tables storing the rows of materialized derived tables/views
- TABLE_SHARE::column_bitmap_size was not set for tmp tables storing
  the rows of materialized derived tables/views.
These could cause crashes or memory overwrite.

If a view/derived table is non-mergeable then the definition of the tmp table
to store the rows for it is created at the prepare stage. In this case if the
view definition uses outer joins and a view column belongs to an inner table
of one of them then the column should be considered as nullable independently
on nullability of the underlying column. If the underlying column happens to be
defined as non-nullable then the function create_tmp_field_from_item rather 
than the function create_tmp_field_from_field should be employed to create
the definition of the interesting column in the tmp table.
 

(testcase for #798597 now crashes)

Fixed several errors in Aria discovered by test case for lp:727869 ma_pagecache.c:2103: find_block: Assertion `block->rlocks == 0
- Fixed assert in transaction log handler when aria_check was run on block-record table that was much bigger than expected.
- Fixed warnings about wrong mutex order between bitmap and intern_lock
- Fixed error in bitmap that could cause two rows to use same block for a block record.
- Fixed wrong test that could cause error if last page for a bitmap was used by a blob.
- Fixed several bugs in pagecache for the case where pagecase had very few blocks and there was a lot of threads competing to get the blocks (very unlikely case).


mysql-test/suite/maria/r/maria-recovery3.result:
  Updated results
sql/mysqld.cc:
  Allow mi_check() to send information messages for log file
storage/maria/ma_bitmap.c:
  Fixed problem with wrong mutex order when bitmap was the first page that was flushed out of page cache
  - Fixed by introducing _ma_bitmap_mark_file_changed() that marks file changed without a bitmap lock.
  - Fixed one case in _ma_change_bitmap_page() where we didn't mark the bitmap changed. This could cause to rows to reuse same block if this was the only change to the bitmap.
  - Split _ma_bitmap_get_page_bits() in two parts to not take a bitmap lock when we already have it
  - Fixed bug in _ma_bitmap_set_full_page_bits() that caused an error if last page for a bitmap was used by a blob
storage/maria/ma_check.c:
  Better handling of wrong file length.
  Fixed bug when we tried to write to transaction log when it was not opened (happened when block record file was bigger than expected)
storage/maria/ma_pagecache.c:
  Fixed several bugs in pagecache for the case where pagecase had very few blocks and there was a lot of threads competing to get the blocks:
  - In link_block() mark a block given to another thread with PCBLOCK_REASSIGNED to ensure that no other threads can start re-using the block
    before the thread that requsted a block.
  - In free_block(), don't reset status for a block that is in re-assign by link_block() (we don't want to loose the PCBLOCK_REASSIGNED flag).
  - Added call to wait_for_flush() when we got a new block in find_block() to ensure that we don't use a block that is beeing flushed by another thread.
  - Moved setting of hits_left and last_hit_time in find_block() to where we assign the block.
  
  
  Code cleanup and making code uniform:
  - Changed a lot of KEYCACHE_DBUG_PRINT to use DBUG_PRINT
  - Streamlined all reporting of 'signal' and 'wait' between threads to be identical.
  - Use thread name instead of thread number (for each match against --debug)
  - Added more DBUG_ENTER, DBUG_PRINT and DBUG_ASSERT()
  - Added more comments
storage/myisam/ha_myisam.cc:
  Only print information about that we make a backup if we are really making a backup.
storage/myisam/mi_check.c:
  Inform mysqld that we are creating a backup of the data file (for inclusion in error log).

- Fixed error when writing a blob to the last page on the bitmap.
- Marked bitmap changed in once case that could cause two rows to use the same blob page.

mysql-test/r/join.result:
  Test case for LP:798597
mysql-test/t/join.test:
  Test case for LP:798597
sql/sql_select.cc:
  In simplify_joins we reset table->maybe_null for outer join tables that can't ever be NULL.
  This caused a conflict between the previously calculated items and the group_buffer against the fields
  in the temporary table that are created as not null thanks to the optimization.
  The fix is to correct the group by items to also be not_null so that they match the used fields and keys.

The function setup_tables should handle table_list elements for
semijoin materialized tables in a special way when executing
a prepared statement for the second time.

The function simple_pred did not take into account that a multiple equality
could include ref items (more exactly items of the class Item_direct_view_ref).
It caused crashes for queries over derived tables or views if the
min/max optimization could be applied to these queries.

The patch for bugs 717577 and 724942 has missed to make adjustments for the
call item_equal->add_const(const_item, orig_field_item) in the function
check_simple_equality that builds multiple equality for a field and a constant.
As a result, when this field happens to be a view field and the corresponding
Item_field object F is wrapped in an Item_direct_view_ref object R the object
F is placed in the multiple equality instead of the object R.
A substitution of an equal item for F potentially can cause very serious
problems and in some cases can lead to crashes of the server.

Removed forgotten EXPLAIN EXTENDED from the test file.

initialize plugins earlier, to support, for example, non-MyISAM mysql.plugin table.

Automerged with 5.3.

- Added regression test with queries over the WORLD database.
- Discovered and fixed several bugs in the related cost calculation
  functionality both in the semijoin and non-semijon subquery code.
- Added DBUG printing of the cost variables used to decide between
  IN-EXISTS and MATERIALIZATION.

Define USE_MARIA_FOR_TMP_TABLES preprocessor constant by default if Aria engine is compiled in.
Use CMake variable WITH_ARIA_TMP_TABLES to control the temp table engine setting.