(null merge of innodb-only changes)

detector". This patch addresses performance regression in OLTP_RO/MyISAM
test on Windows introduced by the fix for bug #56405. Thus it makes
original patch acceptable as a solution for bug #56585 "Slowdown of
readonly sysbench benchmarks (e.g point_select) on Windows 5.5".

With this patch, MySQL will use native Windows condition variables and 
reader-writer locks  if  they are supported by the OS.

This speeds up MyISAM and the effect comes mostly from using native
rwlocks. Native conditions improve scalability with higher number of 
concurrent users in other situations, e.g for prlocks.

Benchmark numbers for this patch as measured on Win2008R2 quad
core machine are attached to the bug report.
( direct link http://bugs.mysql.com/file.php?id=15883 )

Note that currently we require at least Windows7/WS2008R2 for 
reader-writer locks, even though native rwlock is available also on Vista.
Reason is that "trylock" APIs are missing on Vista, and trylock is used in
the server (in a single place in query cache).

While this patch could have been written differently, to enable the native
rwlock optimization also on Vista/WS2008 (e.g using native locks everywhere
but portable implementation in query cache), this would come at the 
expense of the code clarity, as it would introduce a new  "try-able" rwlock
type, to handle Vista case.

Another way to improve performance for the special case 
(OLTP_RO/MYISAM/Vista) would be to eliminate "trylock" usage from server,
 but this is outside of the scope here.


Native conditions variables are used beginning with Vista though the effect
of using condition variables alone is not measurable in this benchmark.
But when used together with native rwlocks on Win7, native conditions improve 
performance in high-concurrency OLTP_RO/MyISAM (128 and more sysbench 
users).

row_search_for_mysql(): Acquire an intention lock on the table
before locking the first record gap.

row_search_for_mysql(): Acquire an intention lock on the table
before locking the first record gap.

conflicts:
   conflict      dbug/dbug.c
   conflict      sql/sql_load.cc

This is a null merge because it only contains InnoDB changes that
originated in mysql-5.1-innodb and have been manually ported into
mysql-5.5-innodb.

This is a manual merge from mysql-5.1-innodb of:

  revision-id: vasil.dimov@oracle.com-20100930102618-s9f9ytbytr3eqw9h
  committer: Vasil Dimov <vasil.dimov@oracle.com>
  timestamp: Thu 2010-09-30 13:26:18 +0300
  message:
    Fix a potential bug when using __sync_lock_test_and_set()

    TYPE __sync_lock_test_and_set (TYPE *ptr, TYPE value, ...)

    it is not documented what happens if the two arguments are of different
    type like it was before: the first one was lock_word_t (byte) and the
    second one was 1 or 0 (int).

    Approved by:	Marko (via IRC)

LOAD DATA into partitioned MyISAM table

Problem was that both partitioning and myisam
used the same table_share->mutex for different protections
(auto inc and repair).

Solved by adding a specific mutex for the partitioning
auto_increment.

Also adding destroying the ha_data structure in
free_table_share (which is to be propagated
into 5.5).

This is a 5.1 ONLY patch, already fixed in 5.5+.

           REBUILD PARTITION under LOCK TABLE

Collapsed patch including updates from the reviews.

In case of failure in ALTER ... PARTITION under LOCK TABLE
the server could crash, due to it had modified the locked
table object, which was not reverted in case of failure,
resulting in a bad table definition used after the failed
command.

Solved by instead of altering the locked table object and
its partition_info struct, creating an internal temporary
intermediate table object used for altering,
just like the non partitioned mysql_alter_table.
So if an error occur before the alter operation is complete,
the original table is not modified at all.
But if the alter operation have succeeded so far that it
must be completed as whole,
the table is properly closed and reopened.
(The completion on failure is done by the ddl_log.)

Added sanity check, similar to the one preventing send without reap