- Do not push index condition if we're using a triggered ref access.

The bug happened because in some cases the function JOIN::exec
did not save the value of TABLE::pre_idx_push_select_cond in
TABLE::select->pre_idx_push_select_cond for the sort table.

Noticed and fixed a bug in the function make_cond_remainder
that builds the remainder condition after extraction of an index
pushdown condition from the where condition. The code
erroneously assumed that the function make_cond_for_table left
the value of ICP_COND_USES_INDEX_ONLY in sub-condition markers.
Adjusted many result files from the regression test suite
after this fix .

The call of the virtual function cancel_pushed_idx_cond in the code of
the function test_if_skip_sort_order was misplaced when backporting the
fix for bug 58816.

Better error message if --log-bin is used without --log-bin-index

mysql-test/lib/v1/mysql-test-run.pl:
  Fixed that test doesn't abort if 'var' points to a deleted directory (common case when using --mem)
sql/mysqld.cc:
  Better error message if --log-bin is used without --log-bin-index

storage/myisam/mi_dbug.c:
  Added mutex to protect open table list while traversing it

- Remove the assert in replace_where_subcondition (the patch has explanation why)

- More test result updates (the errors are the same, the difference is that "at row X" became "at row Y" due to
  queries with semi-joins producing select results in different order)

- More test result updates

- semijoin=on
- firstmatch=on
- loosescan=on

Analysis:
Equality propagation propagated the constant '7' into
args[0] of the Item_in_optimizer that stands for the
"< ANY" predicate. At the same the min/max subquery
rewrite swapped the order of the left and right operands
of the "<" predicate, but used Item_in_subselect::left_expr.

As a result, when the <ANY predicate is executed early in the
execution phase as a contant condition, instead of a constant
right (swapped) argument of the < predicate, there was a field
(t3.a). This field had no data, since the whole predicate is
considered constant, and it is evaluated before any tables are
read. Having junk in the field row buffer produced wrong result

Solution:
Fix create_swap to pick the correct Item_in_optimizer left
argument.

The problem was that merged views has its own nest_level numbering =>
when we compare nest levels we should take into considiration basis (i.e. 0 level),
if it is different then nest levels are not comparable.

Fixed a bug in select_describe.
Adjusted results for affected test cases.

- Make table elimination to actually switch itself on/off in release builds.

- The bug was caused by the following scenario:
  = a quick select is created with get_quick_select_for_ref. The quick 
    select refers to temporary (derived) table. It saves table->file, which
    refers to a ha_heap object.
  = When temp table is populated, ha_heap reaches max. size and is converted
    to a ha_myisam.  However, quick->file remains pointing to where ha_heap 
    was. 
  = Attempt to use the quick select causes crash.
- Fixed by introducing QUICK_SELECT_I::replace_handler(). Note that it will 
  not work for index_merge quick selects. Which is fine, because these
  quick selects are never created for derived tables.

(Failed to reproduce the bug in mariadb-5.3).

The bug was fixed by the patches for LP bugs 668644,702322 that
were applied earlier to the mariadb-5.3 code.

The bug was fixed by the patch for LP bug 694092 that was
applied earlier to the mariadb-5.3 code.

- Fix the compile-time-default value of optimizer_switch printed by mysqld --help --defaults

The function Item_direct_view_ref::fix_fields erroneously did not correct
the value of the flag maybe_null when the view for which the item was
being fixed happened to be an inner table of an outer join.
 

- The problem was that the value of READ_RECORD::file was not updated when the underlying table
  was temporary and was converted from heap to myisam. Resolved by eliminating READ_RECORD::file,
  always use READ_RECORD::table->file

Honor unique/not unique when creating keys for internal tempory tables.
Added new variables to be used to limit how keys are created for internal temporary tables.


include/maria.h:
  Added maria_max_key_length() and maria_max_key_segments()
include/myisam.h:
  Added myisam_max_key_length() and myisam_max_key_segments()
mysql-test/r/mysql.result:
  Drop all used tables
mysql-test/r/subselect4.result:
  Added test case for lp:879939
mysql-test/t/mysql.test:
  Drop all used tables
mysql-test/t/subselect4.test:
  Added test case for lp:879939
sql/mysql_priv.h:
  Added internal_tmp_table_max_key_length and internal_tmp_table_max_key_segments to be used to limit how keys for derived tables are created.
sql/mysqld.cc:
  Added internal_tmp_table_max_key_length and internal_tmp_table_max_key_segments to be used to limit how keys for derived tables are created.
sql/share/errmsg.txt:
  Added new error message for internal errors
sql/sql_select.cc:
  Give error if we try to create a wrong key (this error should never happen)
  Honor unique/not unique when creating keys for internal tempory tables.
storage/maria/ha_maria.cc:
  Added change_table_ptr() to ensure that external_ref points always to the correct table.
  (Not having this caused an assert in the included test)
storage/maria/ha_maria.h:
  Added change_table_ptr() to ensure that external_ref points always to the correct table.
storage/maria/ma_check.c:
  Fixed bug in Duplicate key error printing (now row position is printed correctly)
storage/maria/ma_create.c:
  maria_max_key_length() -> _ma_max_key_length()
storage/maria/ma_info.c:
  Added extern function maria_max_key_length() to calculate the max key length based on current block size.
storage/maria/ma_open.c:
  maria_max_key_length() -> _ma_max_key_length()
storage/maria/maria_def.h:
  maria_max_key_length() -> _ma_max_key_length()
storage/myisam/ha_myisam.cc:
  Added change_table_ptr() to ensure that external_ref points always to the correct table.
  (Not having this caused an assert in the included test)
storage/myisam/ha_myisam.h:
  Added change_table_ptr() to ensure that external_ref points always to the correct table.