merged from mysql-5.5.8-release tree,
revision: ramil@mysql.com-20101203174908-217tdkn150vieha9

when there was one NULL value, AVG(DISTINCT) could forget about other values.
See commit comment of item_sum.cc.

Null merge to from mysql-5.1-bugteam to mysql-5.5-bugteam.
Test case does not exist in 5.5 tree.

Automerging bzr bundle from bug report into latest 
mysql-5.1-bugteam.

            command line clients.

Command line tools like mysqladmin and mysqldump did not recognize
default-auth and plugin-dir options.

Support for these options was found missing in these command line
tools.

Fixed by adding support for the same.

Re-enable fast mutexes on Linux for release builds.

to_binlog -> binlog_stmt.

Adding symbol FN_DIRSEP to Windows as well.

Fixing test case that fails on Windows because .dll is used.

           but the statement is written to binlog

TRUNCATE PARTITION was written to the binlog
even if it failed before calling any partition's
truncate function.

Solved by adding an argument to truncate_partition,
to flag if it should be written to the binlog or not.

It should be written to the binlog when a call to any
partitions truncate function is done.

When installing plugins, there is a missing check
for slash (/) in the path on Windows. Note that on
Windows, both / and \ can be used to separate
directories.

This patch fixes the issue by:
- Adding a FN_DIRSEP symbol for all platforms
  consisting of a string of legal directory
  separators.
- Adding a charset-aware version of strcspn().
- Adding a check_valid_path() function that uses
  my_strcspn() to check if any FN_DIRSEP character
  is in the supplied string.
- Using the check_valid_path() function in
  sql_plugin.cc and sql_udf.cc (which means
  replacing the existing test there).

This is a code cleanup.

The implementation of a storage engine (subclasses of handler) is not supposed
to call my_error() directly inside the engine implementation, 
but only return error codes, and report errors later at the demand
of the sql layer only (if needed), using handler::print_error().

This fix removes misplaced calls to my_error(),
and provide an implementation of print_error() instead.

Given that the sql layer implementation of create table, ha_create_table(),
does not use print_error() but returns ER_CANT_CREATE_TABLE directly,
the return code for create table statements using the performance schema
has changed to ER_CANT_CREATE_TABLE.

Adjusted the test suite accordingly.

Before this fix, the test thread_cache failed with spurious failures.

The test used:
-- disconnect X
-- connect Y

while assuming that connection Y would reuse connection X slot in the thread cache.

For this to happen, the disconnect X operation must be given enough time to complete,
otherwise connect Y can be executed in the server before X actually finishes.

This fix uses wait conditions to make the test execution more controlled,
and more reproductible.

Before this fix, the test myisam_file_io executed:
- (a) an update on setup_instrument to disable non myisam file io instruments
- (b) a truncate on events_waits_history_long
and later
- (c) a select on events_waits_history_long

Surprisingly, events that were supposed to be disabled in (a) and removed in (b)
still were found in (c).

This happened for events such as 
  wait/io/file/innodb/innodb_data_file fil0fil.c: sync  
because the sync was started before (a) and completed after (b),
and as a consequence was added in the performance schema history, as expected.

Presence of these records in the history made the test fail. 

This fix makes the test script more robust to account for extra spill waits records in (c).

This fix affects the test suite only.

Before this fix, performance schema tests dml_*.test could
fail with spurious failure, depending on the table content.

This fix simplifies the SELECT tests in the dml_*.test scripts,
to only verify that the SELECT operation passed the security checks
and succeeded, which was the original intent of the test.

Usage of 
  --replace_column 1 # 2 # 3 # 4 # ...
to discard the test output was replaced by a simpler and more maintainable 
  --disable_result_log
which also work for empty tables.

Fixing the testcase to use the database name
as connected_db instead of 'test' database.

The problem was due to a misuse of GCC asm constraints used to
implement a atomic load. On x86_64, the load was implemented
as a cmpxchg which implicitly uses the eax register as a
source and destination operand, yet the dummy value used for
comparison wasn't being properly loaded into eax (and other
problems).

The core problem is that cmpxchg is unnecessary as a load
on x86_64 as there are other simpler instructions such
as xadd. Even though, such instructions are only used to
have a memory barrier as load and stores are atomic by
definition. Hence, the solution is to explicitly issue the
required CPU and compiler barriers.

integral type. Use intptr which is designed to hold pointer values
and pass it to off_t.