Version for 5.0.
It fixes three problems:
1. The cause of the bug was that we did not check the table version for
 the HANDLER ... READ commands. We did not notice when a table was
 replaced by a new one. This can happen during ALTER TABLE, REPAIR
 TABLE, and OPTIMIZE TABLE (there might be more cases). I call the fix
 for this problem "the primary bug fix".
2. mysql_ha_flush() was not always called with a locked LOCK_open.
 Though the function comment clearly said it must.
 I changed the code so that the locking is done when required. I call
 the fix for this problem "the secondary fix".
3. In 5.0 (not in 4.1 or 4.0) DROP TABLE had a possible deadlock flaw in
 concur with FLUSH TABLES WITH READ LOCK. I call the fix for this
 problem "the 5.0 addendum fix".


include/my_pthread.h:
  Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
  Added a new macro for the 5.0 addendum fix.
mysql-test/r/handler.result:
  Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
  The test result.
mysql-test/t/handler.test:
  Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
  The test case.
sql/lock.cc:
  Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
  Changed a comment which did confuse me and which is not fully
  correct anymore after the 5.0 addendum fix.
  Added an assertion which would fire without the 5.0 addendum fix.
sql/mysql_priv.h:
  Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
  Changed a definition for the secondary fix.
sql/sql_base.cc:
  Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
  Changed function calls for the secondary fix.
sql/sql_class.cc:
  Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
  Changed a function call for the secondary fix.
sql/sql_handler.cc:
  Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
  The first two diffs make the primary bug fix.
  The rest is for the secondary fix.
sql/sql_table.cc:
  Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
  The first diff (four changed places) make the 5.0 addendum fix.
  The other three are changed function calls for the secondary fix.