The idea of the patch
is that every cursor gets its own lock id for table level locking.
Thus cursors are protected from updates performed within the same 
connection. Additionally a list of transient (must be closed at
commit) cursors is maintained and all transient cursors are closed
when necessary. Lastly, this patch adds support for deadlock
timeouts to TLL locking when using cursors.
+ post-review fixes.


include/thr_lock.h:
  - add a notion of lock owner to table level locking. When using
    cursors, lock owner can not be identified by a thread id any more, 
    as we must protect cursors from updates issued within the same 
    connection (thread). So, each cursor has its own lock identifier to 
    use with table level locking.
  - extend return values of thr_lock and thr_multi_lock with
    THR_LOCK_TIMEOUT and THR_LOCK_DEADLOCK, since these conditions
    are now possible (see comments to thr_lock.c)
mysys/thr_lock.c:
  Better support for cursors:
  - use THR_LOCK_OWNER * as lock identifier, not pthread_t.
  - check and return an error for a trivial deadlock case, when an
    update statement is issued to a table locked by a cursor which has 
    been previously opened in the same connection.
  - add support for locking timeouts: with use of cursors, trivial 
    deadlocks can occur. For now the only remedy is the lock wait timeout,
    which is initialized from a new global variable 'table_lock_wait_timeout'
    Example of a deadlock (assuming the storage engine does not downgrade 
    locks):
    con1: open cursor for select * from t1;
    con2: open cursor for select * from t2;
    con1: update t2 set id=id*2;  -- blocked
    con2: update t1 set id=id*2;  -- deadlock
    Lock timeouts are active only if a connection is using cursors.
  - the check in the wait_for_lock loop has been changed from
    data->cond != cond to data->cond != 0. data->cond is zeroed
    in every place it's changed. 
  - added comments
sql/examples/ha_archive.cc:
  - extend the handlerton with the info about cursor behaviour at commit.
sql/examples/ha_archive.h:
  - ctor moved to .cc to make use of archive handlerton
sql/examples/ha_example.cc:
  - add handlerton instance, init handler::ht with it
sql/examples/ha_example.h:
  - ctor moved to .cc to make use of ha_example handlerton
sql/examples/ha_tina.cc:
  - add handlerton instance, init handler::ht with it
sql/examples/ha_tina.h:
  - ctor moved to .cc to make use of CSV handlerton
sql/ha_berkeley.cc:
  - init handlerton::flags and handler::ht
sql/ha_berkeley.h:
  - ctor moved to .cc to make use of BerkeleyDB handlerton
sql/ha_blackhole.cc:
  - add handlerton instance, init handler::ht with it
sql/ha_blackhole.h:
  - ctor moved to .cc to make use of blackhole handlerton
sql/ha_federated.cc:
  - add handlerton instance, init handler::ht with it
sql/ha_federated.h:
  - ctor moved to .cc to make use of federated handlerton
sql/ha_heap.cc:
  - add handlerton instance, init handler::ht with it
sql/ha_heap.h:
  - ctor moved to .cc to make use of ha_heap handlerton
sql/ha_innodb.cc:
  - init handlerton::flags and handler::ht of innobase storage engine
sql/ha_innodb.h:
  - ctor moved to .cc to make use of archive handlerton
sql/ha_myisam.cc:
  - add handlerton instance, init handler::ht with it
sql/ha_myisam.h:
  - ctor moved to .cc to make use of MyISAM handlerton
sql/ha_myisammrg.cc:
  - init handler::ht in the ctor
sql/ha_myisammrg.h:
  - ctor moved to .cc to make use of MyISAM MERGE handlerton
sql/ha_ndbcluster.cc:
  - init handlerton::flags and handler::ht
sql/handler.cc:
  - drop support for ISAM storage engine, which was removed from 5.0
  - close all "transient" cursors at COMMIT/ROLLBACK. A "transient"
    SQL level cursor is a cursor that uses tables that have a transaction-
    specific state.
sql/handler.h:
  - extend struct handlerton with flags, add handlerton *ht to every
    handler instance.
sql/lock.cc:
  - extend mysql_lock_tables to send error to the client if 
    thr_multi_lock returns a timeout or a deadlock error.
sql/mysqld.cc:
  - add server option --table_lock_wait_timeout (in seconds)
sql/set_var.cc:
  - add new global variable 'table_lock_wait_timeout' to specify
  a wait timeout for table-level locks of MySQL (in seconds). The default
  timeout is 50 seconds. The timeout is active only if the connection
  has open cursors.
sql/sql_class.cc:
  - implement Statement_map::close_transient_cursors
  - safety suggests that we need an assert ensuring 
   llock_info->n_cursors is functioning properly, adjust destruction of
   the Statement_map to allow such assert in THD::~THD
sql/sql_class.h:
  - add support for Cursors registry to Statement map.
sql/sql_prepare.cc:
  - maintain a list of cursors that must be closed at commit/rollback.
sql/sql_select.cc:
  - extend class Cursor to support specific at-COMMIT/ROLLBACK behavior.
  If a cursor uses tables of a storage engine that 
  invalidates all open tables at COMMIT/ROLLBACK, it must be closed
  before COMMIT/ROLLBACK is executed.
sql/sql_select.h:
  - add an own lock_id and commit/rollback status flag to class Cursor
tests/mysql_client_test.c:
  A test case for Bug#10760 and complementary issues: test a simple
  deadlock case too.
mysql-test/var:
  New BitKeeper file ``mysql-test/var''