The problem was that mysql_stmt_next_result() (new to 5.5)
was not properly updated.

libmysql/libmysql.c:
  mysql_stmt_next_result() modified: set mysql->status= MYSQL_STATUS_STATEMENT_GET_RESULT before return
  if there is a result set.

      
The EXISTS transformation has additional switches to catch the known corner
cases that appear when transforming an IN predicate into EXISTS. Guarded
conditions are used which are deactivated when a NULL value is seen in the
outer expression's row. When the inner query block supplies NULL values,
however, they are filtered out because no distinction is made between the
guarded conditions; guarded NOT x IS NULL conditions in the HAVING clause that
filter out NULL values cannot be de-activated in isolation from those that
match values or from the outer expression or NULL's.

The above problem is handled by making the guarded conditions remember whether
they have rejected a NULL value or not, and index access methods are taking
this into account as well. 

The bug consisted of 

1) Not resetting the property for every nested loop iteration on the inner
   query's result.

2) Not propagating the NULL result properly from inner query to IN optimizer.

3) A hack that may or may not have been needed at some point. According to a
   comment it was aimed to fix #2 by returning NULL when FALSE was actually
   the result. This caused failures when #2 was properly fixed. The hack is
   now removed.

The fix resolves all three points.

multi-table UPDATE IGNORE.
The problem was that if there was an active SELECT statement
during trigger execution, an error risen during the execution
may cause a crash. The fix is to temporary reset LEX::current_select
before trigger execution and restore it afterwards. This way
errors risen during the trigger execution are processed as
if there was no active SELECT.

mysql-test/r/trigger_notembedded.result:
  added test case result for bug #55421.
mysql-test/t/trigger_notembedded.test:
  added test case for bug #55421.
sql/sql_trigger.cc:
  Reset thd->lex->current_select before start trigger execution
  and restore its original value after execution is finished.
  This is neccessery in order to set error status in 
  diagnostic_area in case of trigger execution failure.

inited==INDEX

When an error occurs while sending the data in a temporary table there was no
cleanup performed. This caused a failed assertion in the case when different
access methods were used for populating the table vs. retrieving the data from
the table if IGNORE was specified and sql_safe_updates = 0. In this case
execution continues, but the handler expects to continue with the access
method used for row retrieval.

Fixed by doing the cleanup even if errors occur.

for a prepared statement.

include/mysql.h:
  enumerator MYSQL_STATUS_STATEMENT_GET_RESULT was added
  into mysql_status enum.
include/mysql.h.pp:
  enumerator MYSQL_STATUS_STATEMENT_GET_RESULT was added
  into mysql_status enum.
libmysql/libmysql.c:
  Introduce a separate mysql state to distinguish the situation
  when we have a binary result set pending on the server from the
  situation when the result set is in text protocol.
  execute() modified: if mysql->status == MYSQL_STATUS_GET_RESULT
  before return then set it to value MYSQL_STATUS_STATEMENT_GET_RESULT.
  stmt_read_row_unbuffered() and mysql_stmt_store_result()
  were modified: added checking for mysql->status against
  MYSQL_STATUS_STATEMENT_GET_RESULT value instead of MYSQL_STATUS_GET_RESULT.
tests/mysql_client_test.c:
  added test_bug47485()

          case than in corr index".
      
Server was unable to find existing or explicitly created supporting
index for foreign key if corresponding statement clause used field
names in case different than one used in key specification and created
yet another supporting index.
In cases when name of constraint (and thus name of generated index)
was the same as name of existing/explicitly created index this led
to duplicate key name error.
      
The problem was that unlike all other code Key_part_spec::operator==()
compared field names in case sensitive fashion. As result routines
responsible for getting rid of redundant generated supporting indexes
for foreign key were not working properly for versions of field names
using different cases.

(backported from mysql-trunk)


sql/sql_class.cc:
  Make field name comparison case-insensitive like it is
  in the rest of server.

Make the my_compiler.h header, like my_attribute.h, part of
the distribution. This is required due to the dependency of
the former on the latter (which can undefine __attribute__).

            "Access compatibility" syntax

The "wild" "DELETE FROM table_name.* ... USING ..." syntax
for multi-table DELETE statements is documented but it was
lost in the fix for the bug 30234.

The table_ident_opt_wild parser rule has been added
to restore the lost syntax.


mysql-test/r/delete.result:
  Test case for bug #53034.
mysql-test/t/delete.test:
  Test case for bug #53034.
sql/sql_yacc.yy:
  Bug #53034: Multiple-table DELETE statements not accepting
              "Access compatibility" syntax
  
  The table_ident_opt_wild parser rule has been added
  to restore the lost syntax.
  Note: simple extending of table_ident with opt_wild in
  the table_alias_ref rule is not acceptable, because
  a) it adds one conflict more and b) this conflict resolves
  in the inappropriate way.

so test case has to be updated.

Check for number of line strings in the incoming polygon data (wkb) and
for number of points in the incoming linestring wkb.



mysql-test/r/gis.result:
  Fix for bug #51875: crash when loading data into geometry function polyfromwkb
    - test result.
mysql-test/t/gis.test:
  Fix for bug #51875: crash when loading data into geometry function polyfromwkb
    - test case.
sql/spatial.cc:
  Fix for bug #51875: crash when loading data into geometry function polyfromwkb
    - creating a polygon from wkb check for number of line strings,
    - creating a linestring from wkb check for number of line points.

            == MYSQL_TYPE_LONGLONG

A MIN/MAX() function with a subquery as its argument could lead
to a debug assertion on debug builds or wrong data on release
ones.

The problem was a combination of the following factors:

- Item_sum_hybrid::fix_fields() might use the argument
(args[0]) to calculate 'hybrid_field_type' which was later used
to decide how the data should be sent to the client.

- Item_sum::make_field() might use the argument again to
calculate the field's type when sending result set metadata to
the client.

- The argument could be changed in between these two calls via
  Item::set_arg() leading to inconsistent metadata being
  reported.

Here is what was happening for the bug's test case:

1. Item_sum_hybrid::fix_fields() calculates hybrid_field_type
as MYSQL_TYPE_LONGLONG based on args[0] which is an
Item::SUBSELECT_ITEM at that time.

2. A temporary table is created to execute the
query. create_tmp_field_from_item() creates a Field_long object
according to the subselect's max_length.

3. The subselect item in Item_sum_hybrid is replaced by the
Item_field object referencing the newly created Field_long.

4. Item_sum::make_field() rightfully returns the
MYSQL_TYPE_LONG type when calculating the result set metadata.

5. When sending the actual data, Item::send() relies on the
virtual field_type() function which in our case returns
previously calculated hybrid_field_type == MYSQL_TYPE_LONGLONG.

It looks like the only solution is to never refer to the
argument's metadata after the result metadata has been
calculated in fix_fields(), since the argument itself may be
different by then. In this sense, Item_sum::make_field() should
never be used, because it may rely on the argument's metadata
and is only called after fix_fields(). The "default"
implementation in Item::make_field() should be used instead as
it relies only on field_type(), but not on the argument's type.

Fixed by removing Item_sum::make_field() so that the superclass
implementation Item::make_field() is always used.

mysql-test/r/func_group.result:
  Added a test case for bug #54465.
mysql-test/t/func_group.test:
  Added a test case for bug #54465.
sql/item_sum.cc:
  Removed Item_sum::make_field() so that the superclass
  implementation Item::make_field() is always used.
sql/item_sum.h:
  Removed Item_sum::make_field() so that the superclass
  implementation Item::make_field() is always used.

Free memory allocated by the server for all plugins,
with or without deinit() method.

            not tested by ABI check

plugin_audit.h and plugin_ftparser.h are now subject
for ABI check. plugin.h is now tested implicitly.

Also fixed broken ABI check cmake rules.

Makefile.am:
  plugin_audit.h and plugin_ftparser.h are now subject
  for ABI check. plugin.h is now tested implicitly.
cmake/abi_check.cmake:
  plugin_audit.h and plugin_ftparser.h are now subject
  for ABI check. plugin.h is now tested implicitly.
  
  Also fixed broken ABI check rules: -DMYSQL_ABI_CHECK is
  compiler (not cmake) definition, incorrect definitions
  were passed to do_abi_check.cmake for abi_check_all rule.
cmake/do_abi_check.cmake:
  Inform sources that we do ABI check.
include/mysql/plugin.h.pp:
  plugin.h is now tested implicitly.
include/mysql/plugin_audit.h.pp:
  plugin_audit.h is now subject for ABI check.
include/mysql/plugin_ftparser.h.pp:
  plugin_ftparser.h is now subject for ABI check.