The convert_constant_item function converts a constant to integer using
field for condition like 'field = a_constant'. In some cases the
convert_constant_item is called for a subquery when outer select is already
being executed, so convert_constant_item saves field's value to prevent its
corruption. For EXPLAIN and at the prepare phase field's value isn't
initialized yet, thus when convert_constant_item tries to restore saved
value it fails assertion.

Now the convert_constant_item doesn't save/restore field's value if it's
haven't been read yet. Outer constant values are always saved.

  Bug#39848 events_bugs fails sporadically on pushbuild
            (missing rows in table event_log)
     Details: Reimplement the subtest for BUG 28924
              - check if the number of rows within the table
                event_log changes but don't print rows
                because the number varies depending on
                load on testing box
              - shift DROP USER befor DROP EVENT
                = Subtest fits again to old bug
              - remove no more needed comments + variables
  Bug#39863 events_bugs fails sporadically on pushbuild 
            (extra processes in I_S.PROCESSLIST)
     Details: Abort with appropriate message to the protocol if
              release_lock() does not has the intended effect.
              This cannot prevent problems caused by the probably
              buggy release_lock() but it reveals if we had a
              problem in this area.
  Bug#39978 main.events_bugs does not clean up
     Detail: Restore global.event_scheduler = ON at end of test
  Bug#39569 events_bugs fails sporadically on pushbuild
            (should have failed with errno 1539)
     Detail: Set $wait_timeout to 4 instead of 2
- Fix two instabilities (result sets pulled from processlist in
  subtest for bug 16407) which were found during tests with high
  parallel I/O load
- Minor improvements of formatting
  Details:
  - Add comments
  - Remove tabs and trailing blanks
  - Add line breaks for better readability

updating two test results.

correct text describing the --plugin-load option to mysqld

The partitioning clause is only a very long single line, which is very
hard to interpret for a human. This patch breaks the partitioning
syntax into one line for the partitioning type, and one line per
partition/subpartition.

TRUNCATE TABLE for InnoDB tables returned a count showing an approximation
of the number of rows affected to gain efficiency.
Now the statement always returns 0 rows affected for clarity.

a test on the bug page does not reveal the problem with the latest trees.

Adding the test to the rpl suite in order to monitor regression.

implicit command which isn't completed immediately.

Problem was that partitioning cached the table flags.
These flags could change due to TRANSACTION LEVEL changes.
Solution was to remove the cache and always return the table flags
from the first partition (if the handler was initialized).

    #ifdef HAVE_purify removed

per-file comments:
  mysql-test/t/partition_not_windows.test
Bug#39102 valgrind build does not compile in realpath, which make DATA/INDEX DIR fail 
    test reenabled

  mysys/my_symlink.c
Bug#39102 valgrind build does not compile in realpath, which make DATA/INDEX DIR fail 
  superfluous ifdef removed, comments fixed

A string buffers which were included in the 'view' data structure
were allocated on the stack, causing an invalid pointer when used
after the function returned.
The fix: use copy of values for view->md5 & view->queries

      
The convert_constant_item function converts a constant to integer using
field for condition like 'field = a_constant'. When the convert_constant_item
is called for a subquery the outer select is already being executed, so
convert_constant_item saves field's value to prevent its corruption.
For EXPLAIN field's value isn't initialized thus when convert_constant_item
tries to restore saved value it fails assertion.
      
Now the convert_constant_item doesn't save/restore field's value
for EXPLAIN.

The abi_check target instroduced as part of WL#4380 verifies
changes to mysql.h. mysql.h in turn includes mysql_version.h.
mysql_version.h is a file that is generated during the configure
phase. We must ensure that mysql_version.h is cleaned only during
distclean and not during clean.

1. Replace --sleep by wait_* primitive
2. Vertical output for SHOW SLAVE STATUS
3. Updated result file