The problem is that select queries executed concurrently with
a concurrent insert on a MyISAM table could be cached if the
select started after the query cache invalidation but before
the unlock of tables performed by the concurrent insert. This
race could happen because the concurrent insert was failing
to prevent cache of select queries happening at the same time.

The solution is to add a 'uncacheable' status flag to signal
that a concurrent insert is being performed on the table and
that queries executing at the same time shouldn't cache the
results.

mysql-test/r/query_cache_debug.result:
  Add test case result for Bug#41098
mysql-test/t/disabled.def:
  Re-enable test case.
mysql-test/t/query_cache_debug.test:
  Add test case for Bug#41098
sql/sql_cache.cc:
  Debug sync point for regression testing purposes.
sql/sql_insert.cc:
  Remove meaningless query cache invalidate. There is already
  a preceding invalidate for queries that started before the
  concurrent insert.
storage/myisam/ha_myisam.cc:
  Check for a active concurrent insert.
storage/myisam/mi_locking.c:
  Signal the start of a concurrent insert. Flag is zeroed once
  the state is updated back.
storage/myisam/myisamdef.h:
  Add flag to signal a active concurrent insert.

1. Constant values of binlog positions replaced by seeking them in binlog/relay log.
2. Updated result file

connections
The problem is that tables can enter open table cache for a thread without 
being properly cleaned up. This can happen if make_join_statistics() fails 
to read a const table because of e.g. a deadlock. It does set a member of 
TABLE structure to a value it allocates, but doesn't clean-up this setting 
on error nor does it set the rest of the members in JOIN to allow for 
automatic cleanup.
As a result when such an error occurs and the next statement depends re-uses 
the table from the open tables cache it will get it with this 
TABLE::reginfo.join_tab pointing to a memory area that's freed.
Fixed by making sure make_join_statistics() cleans up TABLE::reginfo.join_tab 
on error.

mysql-test/r/innodb_mysql.result:
  Bug #42419: test case
mysql-test/t/innodb_mysql-master.opt:
  Bug #42419: increase the timeout so it covers te conservative 
  sleep 3 in the test
mysql-test/t/innodb_mysql.test:
  Bug #42419: test case
sql/sql_select.cc:
  Bug #42419: clean up the members of TABLE on failure in 
          make_join_statisitcs()

In case of ROW item each compared pair does not
check if argumet collations can be aggregated and
thus appropiriate item conversion does not happen.
The fix is to add the check and convertion for ROW
pairs.


mysql-test/r/row.result:
  test result
mysql-test/t/row.test:
  test case
sql/item.cc:
  added agg_item_set_converter() function which was a part of
  agg_item_charsets() func. The only difference is that
  agg_item_set_converter() checks and converts items 
  using already known collation.
sql/item.h:
  added agg_item_set_converter() function
sql/item_cmpfunc.cc:
  In case of ROW item each compared pair does not
  check if argumet collations can be aggregated and
  thus appropiriate item conversion does not happen.
  The fix is to add the check and convertion for ROW
  pairs.

configure.in

Replacing AC_CHECK_FUNC+AC_CHECK_LIB combination with
AC_SEARCH_LIBS.

returns short string value. 
 
Multibyte character sets were not taken into account when 
calculating max_length in Item_param::convert_str_value(). As a 
result, string parameters of a prepared statement could be 
truncated later when calculating string length in characters by 
dividing length in bytes by the charset's mbmaxlen value (e.g. in 
Field_varstring::store()). 
 
Fixed by taking charset's mbmaxlen into account when calculating 
max_length in Item_param::convert_str_value().


sql/item.cc:
  Multiply string's length in characters by charset's mbmaxlen when 
  calculating max_length.
tests/mysql_client_test.c:
  Added a test case for bug #41078.

      
Removed the misleading "NOTE:" from the \h command. 

client/mysql.cc:
  Bug #26724: removed the misleading note from the \h command

replace wild_case_compare with my_wildcmp which is multibyte safe function


mysql-test/r/lowercase_utf8.result:
  test result
mysql-test/t/lowercase_utf8-master.opt:
  test case
mysql-test/t/lowercase_utf8.test:
  test case
sql/sql_show.cc:
  replace wild_case_compare with my_wildcmp which is multibyte safe function

Substitute all references of MySQL version "5.2" to "6.0" in
deprecation warning messages.Deprecated constructs are being
removed in the 6.0 tree.

mysql-test/t/gis.test:
  IA64 gcc backend lacks -fno-fused-madd option, so we have to adjust results.

mysql-test/r/type_float.result:
  Added missing DROP TABLE.

mysql-test/r/parser.result:
  Take additional precision into account.

mysql-test/suite/funcs_1/r/memory_func_view.result:
  Take additional precision into account.
mysql-test/suite/funcs_1/r/memory_views.result:
  Take additional precision into account.
mysql-test/suite/funcs_1/r/myisam_func_view.result:
  Take additional precision into account.
mysql-test/suite/funcs_1/r/myisam_views.result:
  Take additional precision into account.

mysql-test/r/bdb_gis.result:
  Take additional precision into account.
mysql-test/r/ndb_gis.result:
  Take additional precision into account.
mysql-test/t/type_float.test:
  Added missing DROP TABLE.