back-ported the patch for bug #13256831 from mysql-5.6 code line.

  Here's the comment this patch was provided with:

  Fixed bug#13256831 - ERROR 1032 (HY000): CAN'T FIND RECORD.

  This bug only occurs if a user tries to update a base table using
  an updatable view and this view was created as a join for which
  the clause 'WITH CHECK OPTION' was specified.

  The reason for the bug was that when such an update was
  executed, row positions were not properly handled for tables
  that were not updated but had constraints that had to be
  checked due to the 'WITH CHECK OPTION' clause.

  The reason for the bug was that when such update is executed
  then for tables specified in the view definition and
  also listed in the 'WITH CHECK OPTION' clause the positioning to
  row being updated is not performed.

Removed unused result files.

Add a testcase and backport this fix:

Bug#14338686: MYSQL IS GENERATING DIFFERENT AND SLOWER
              (IN NEWER VERSIONS) EXECUTION PLAN
PROBLEM:
While checking for an index to sort for the order by clause
in this query
"SELECT datestamp FROM contractStatusHistory WHERE
contract_id = contracts.id ORDER BY datestamp asc limit 1;"

we do not calculate the number of rows to be examined correctly.
As a result we choose index 'idx_contractStatusHistory_datestamp'
defined on the 'datestamp' field, rather than choosing index
'contract_id'. And hence the lower performance.

ANALYSIS:
While checking if an index is present to give the records in
sorted order(datestamp), we consider the selectivity of the
'ref_key'(contract_id here) using 'table->quick_condition_rows'.
'ref_key' here can be an index from 'REF_ACCESS' or from 'RANGE'.

As this is a 'REF_ACCESS', 'table->quick_condition_rows' is not
set to the actual value which is 2. Instead is set to the number
of tuples present in the table indicating that every row that
is selected would be satisfying the condition present in the query.

Hence, the selectivity becomes 1 even when we choose the index
on the order by column instead of the join_condition.

But, in reality as only 2 rows satisy the condition, we need to
examine half of the entire data set to get one tuple when we
choose index on the order by column.
Had we chosen the 'REF_ACCESS' we would have examined only 2 tuples.
Hence the delay in executing the query specified.
  
FIX:
While calculating the selectivity of the ref_key:
For REF_ACCESS consider quick_rows[ref_key] if range 
optimizer has an estimate for this key. Else consider 
'rec_per_key' statistic.
For RANGE ACCESS consider 'table->quick_condition_rows'.

- Make JOIN::const_key_parts include keyparts for which 
  the WHERE clause has an equality in form 
  "t.key_part=reference_outside_this_select"
- This allows to avoid filesort'ing in some cases (and also 
  avoid a difficult choice between using filesort or using an index)

10.0 variation of the problem was that system tables were altered
during mysql_upgrade process using old (smaller) column lengths. 
At the end the tables were altered again, so the structure was restored,
but if there were long values before the upgrade, they were truncated.
Fixed by using correct column length in alter statements.

MDEV-5401: Wrong result (missing row) on a 2nd execution of PS with exists_to_in=on, MERGE view or a SELECT SQ

The problem was that the view substitute its fields (on prepare) with reverting the change after execution. After prepare on optimization exists2in convertion substituted arguments of '=' with constsnt '1', but then one of the arguments of '=' was reverted to the view field reference.This lead to incorrect WHERE condition on the second execution.

To fix the problem we replace whole '=' with '1' permannently.

We need to use mysql_cond_broadcast() rather than _signal for
COND_thread_count, as there can be multiple waiters.

Thanks to Pavel Ivanov for reporting both the problem and the
solution.

The code did not correctly handle the update of position for Rotate events in the
binlog/relaylog when using parallel replication.

MDEV-5984: EITS: Incorrect filtered% value for single-table select with range access
- Fix calculate_cond_selectivity_for_table() to work correctly with range accesses 
  over multi-component keys:
  = First, take selectivity of all possible range scans into account. Remember which 
    fields were used bt the range scans.
  = Then, calculate selectivity produced by sargable predicates on fields. If a 
    field was used in a possible range access, assume its selectivity is already
    taken into account.
- Fix table_cond_selectivity(): when quick select is used, selectivity of
  COND(table) is taken into account in matching_candidates_in_table(). In
  table_cond_selectivity() we should not apply it for the second time.

asserts can be conditionally compiled out.

see MDEV-5981

another post-fix patch for MDEV-5850: MySQL Bug#21317: SHOW CREATE DATABASE does not obey to lower_case_table_names
(for case-insensitive filesystems)

sql/events.cc:
  for "SHOW EVENTS IN db_name"
sql/sp_head.h:
  for "CREATE EVENT", and everything SP-related
sql/sql_acl.cc:
  privilege check for mysql_change_db()
sql/sql_db.cc:
  for metadata locking of db names
sql/sql_parse.cc:
  any_db is a constant, it is not writable
sql/sql_show.cc:
  for SHOW CREATE TRIGGER and other trigger-related statements

MDEV-5971 Asymmetry between CAST(DATE'2001-00-00') to INT and TO CHAR in prepared statements

Consistently set maybe_null flag, even not-NULL temporal literal may become NULL
in the restrictive sql_mode.

fix uninit variable

Fixed that the we don't change CREATE to CREATE OR REPLACE, except if the slave removed an existing table as part of CREATE.
This will help the following replicaition scenario:
MariaDB 10.0 master (statement replication) -> MariaDB 10.0 slave (row based replication) -> MySQL or MariaDB 5.x slave


mysql-test/r/mysqld--help.result:
  Updated help text
mysql-test/suite/rpl/r/create_or_replace_mix.result:
  Added more tests
mysql-test/suite/rpl/r/create_or_replace_row.result:
  Added more tests
mysql-test/suite/rpl/r/create_or_replace_statement.result:
  Added more tests
mysql-test/suite/rpl/t/create_or_replace.inc:
  Added more tests
sql/handler.h:
  Added org_options so that we can detect what come from the query and what was possible added later.
sql/sql_insert.cc:
  Only write CREATE OR REPLACE if was originally specified or if we delete a conflicting table as part of create
sql/sql_parse.cc:
  Remember orginal create options
sql/sql_table.cc:
  Only write CREATE OR REPLACE if was originally specified or if we delete a conflicting table as part of create
sql/sys_vars.cc:
  Updated help text

            TABLE_SHARE::visit_subgraph

tc_acquire_table() is not ready to update TABLE::in_use without mutex:
thr1: table= free_tables.pop_front(); // table->in_use is 0
thr2: tdc_remove_table();
thr2: find_deadlock(); // assert(table->in_use != 0)
thr1: table->in_use= thd;

Protect update of TABLE::in_use by LOCK_table_share.

mysql.column_stats.

- Fix valgrind failure: don't touch table_list->master_had_triggers 
  when RBR_TRIGGERS is not compiled in.

post-fix patch for MDEV-5850: MySQL Bug#21317: SHOW CREATE DATABASE does not obey to lower_case_table_names

- Show a line with "Engine-independent statistics collected" when ANALYZE command
  caused EITS statistics to be recollected.

  to use named pipe on Windows by specifying the host as '.'
  This addresses MDEV-5952.
modified:
  storage/connect/myconn.cpp

- Clean some unused code
modified:
  storage/connect/connect.cc
  storage/connect/connect.h
  storage/connect/ha_connect.cc
  storage/connect/ha_connect.h

- Dont substract unsigned numbers, use correct calculations.
- (there is no testcase because effort is required to come up with it)

- Move [some] engine-agnostic tests from t/selectivity.test to t/selectivity_no_engine.test
- Move Histogram::point_selectivity to sql_statistics.cc