Bug#38435 - LONG Microseconds cause MySQL to fail a CAST to DATETIME or DATE

Parsing of optional microsecond part in datetime did not
fail gracefully when field width was larger than the allowed
six places.

Now handles up to the correct six places, and disregards
any extra digits without messing up what we've already got.

- /tmp directory is not guaranteed to exist on Windows. 
Use the value of environment variable TEMP here

This involves just the tag, no file changes - they were all present before.

In 37553 we declared longlong results for
class Item_str_timefunc as per comments/docs,
but didn't add a method for that. And the
default just wasn't good enough for some
cases.

Changeset adds dedicated val_int() to class.

- remove the disbling of all ssl_* tests now when certs are fixed.

The problem is that MySQL use of pthread_setschedprio is not
supported by i5/OS and the default system behavior for unsupported
calls is to emit a SIGILL signal which causes the server to
abort.

The solution is to treat the pthread_setschedprio as inexistent
when compiling binaries for i5/OS. This also does not invalidate
the fix for bug 38477 as the only supported dispatch class is
SCHED_OTHER (which is passed to pthread_setschedparam).

 - Allow the new process to break away from any job that this
   process is part of so that it can be assigned to the new JobObject
   we just created. This is safe since the new JobObject is created with
   the JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE flag, making sure it will be
   terminated when the last handle to it is closed(which is owned by
   this process).

+ minor improvements

Documented behaviour was broken by the patch for bug 33699
that actually is not a bug.

This fix reverts patch for bug 33699 and reverts the
UPDATE of NOT NULL field with NULL query to old
behavior.

            ORDER BY could cause a server crash

Dependent subqueries like

  SELECT COUNT(*) FROM t1, t2 WHERE t2.b
   IN (SELECT DISTINCT t2.b FROM t2 WHERE t2.b = t1.a)

caused a memory leak proportional to the
number of outer rows.


The make_simple_join() function has been modified to
JOIN class method to store join_tab_reexec and
table_reexec values in the parent join only
(make_simple_join of tmp_join may access these values
via 'this' pointer of the parent JOIN).

NOTE: this patch doesn't include standard test case (this is
"out of memory" bug). See bug #42037 page for test cases.

Problem: some queries using NAME_CONST(.. COLLATE ...)
lead to server crash due to failed type cast.

Fix: return the underlying item's type in case of
NAME_CONST(.. COLLATE ...) to avoid wrong casting.

   code backported from 6.0


per-file messages:
  include/my_global.h
    Remove SC_MAXWIDTH. This is unused and irrelevant nowadays.
  include/my_sys.h
    Remove errbuf declaration and unused definitions.
  mysys/my_error.c
    Remove errbuf definition and move and adjust ERRMSGSIZE.
  mysys/my_init.c
    Declare buffer on the stack and use my_snprintf.
  mysys/safemalloc.c
    Use size explicitly. It's more than enough for the message at hand.
  sql/sql_error.cc
    Use size explicitly. It's more than enough for the message at hand.
  sql/sql_parse.cc
    Declare buffer on the stack. Use my_snprintf as it will result in
    less stack space being used than by a system provided sprintf --
    this allows us to put the buffer on the stack without causing much
    trouble. Also, the use of errbuff here was not thread-safe as the
    function can be entered concurrently from multiple threads.
  sql/sql_table.cc
    Use MYSQL_ERRMSG_SIZE. Extra space is not needed as my_snprintf will
    nul terminate strings.
  storage/myisam/ha_myisam.cc
Use MYSQL_ERRMSG_SIZE.
  sql/share/errmsg.txt
    Error message truncation in test "innodb" in embedded mode
    filename in the error message can safely take up to 210 symbols.