On QA request, adding test that causes new code to be called. 
Even if we cannot validate the result, this will at least increase the code coverage.

Original revision:
------------------------------------------------------------
revision-id: kent.boortz@sun.com-20100204182709-dw1dwpglkd5qrehb
committer: Kent Boortz <kent.boortz@sun.com>
branch nick: mysql-5.1-bugteam
timestamp: Thu 2010-02-04 19:27:09 +0100
message:
  LT_INIT and LT_PREREQ was added in libtool 2.2 2008, a bit too
  recent, switched back to the older AC_PROG_LIBTOOL
------------------------------------------------------------

Patch contributed by Alex Budovski.

Conflicts:
  - sql/sys_vars.cc

Null merge the fix for Bug#49894

The number for MYSQL_REPLICATION_PLUGIN was shifted when backporting
because MYSQL_AUDIT_PLUGIN was not backported.

This problem is fixed by backporting only the number of audit plugin
and print an error when trying to load audit plugins. Note that
replication plugins compiled against old MYSQL_REPLICATION_PLUGIN
number will also be recognized as audit plugin and be rejected.

left unchanged on patch for BUG#50192.

Conflicts:
  - configure.in

Conflicts:
  - configure.in

Conflicts:
  - sql/sql_show.cc

Conflicts:
  - sql/sql_select.cc

Conflicts:
  - configure.in
  - mysql-test/include/setup_fake_relay_log.inc
  - sql/sql_select.cc

           
Conflicts
=========
Text conflict in sql/repl_failsafe.cc

Additional changes
==================
Replace references to pthread_mutex with mysql_mutex

fails in PB sporadically)
      
The IO thread can concurrently access the relay log IO_CACHE
while another thread is performing an FLUSH LOGS procedure.
      
FLUSH LOGS closes and reopens the relay log and while doing so it
(re)initializes its IO_CACHE. During this procedure the IO_CACHE
mutex is also reinitialized, which can cause problems if some
other thread (namely the IO THREAD) is concurrently accessing it
at the time .
      
This patch fixes the problem by extending the interface of the
flush_master_info function to also include a second paramater, 
"need_relay_log_lock", stating whether the thread should grab the 
relay log lock or not before actually flushing the relay log. 
Also, IO thread now calls flush_master_info with this flag set 
when it flushes master info with in the event read_event loop.

Finally, we also increase loop time in rpl_heartbeat_basic test 
case, so that the number of calls to flush logs doubles, stressing
this part of the code a little more.

Conflicts:
  - sql/mysqld.cc

Conflicts:
  - mysql-test/t/bug46080.test