a SELECT doesn't cause ROLLBACK of statem".

The idea of the fix is to ensure that we always commit the current
statement at the end of dispatch_command(). In order to not issue
redundant disc syncs, an optimization of the two-phase commit
protocol is implemented to bypass the two phase commit if
the transaction is read-only.


mysql-test/suite/binlog/r/binlog_row_mix_innodb_myisam.result:
  Update test results.
mysql-test/suite/binlog/r/binlog_stm_mix_innodb_myisam.result:
  Update test results.
mysql-test/suite/rpl_ndb/t/disabled.def:
  Disable the tests, for which this changeset reveals a bug:
  the injector thread does not always add 'statement commit' to the
  rows injected in circular replication set up.
  To be investigated separately.
sql/ha_ndbcluster_binlog.cc:
  Add close_thread_tables() to run_query: this ensures
  that all tables are closed and there is no pending statement transaction.
sql/handler.cc:
  Implement optimisation of read-only transactions.
  If a transaction consists only of DML statements that do not change
  data, we do not perform a two-phase commit for it 
  (run one phase commit only).
sql/handler.h:
  Implement optimisation of read-only transactions.
  If a transaction consists only of DML statements that do not change
  data, we do not perform a two-phase commit for it 
  (run one phase commit only).
sql/log.cc:
  Mark the binlog transaction read-write whenever it's started.
  We never read from binlog, so it's safe and least intrusive to add
  this mark up here.
sql/log_event.cc:
  Update to the new layout of thd->transaction.
sql/rpl_injector.cc:
  Always commit statement transaction before committing the global one.
sql/sp.cc:
  Ad comments.
sql/sp_head.cc:
  Add comments.
sql/sql_base.cc:
  Commit transaction at the end of the statement. Always.
sql/sql_class.cc:
  Update thd_ha_data to return the right pointer in the new layout.
  
  Fix select_dumpvar::send_data to properly return operation status.
  A test case from commit.inc would lead to an assertion failure in the 
  diagnostics area (double assignment). Not test otherwise by the test suite.
sql/sql_class.h:
  Implement a new layout of storage engine transaction info in which 
  it is easy to access all members related to the handlerton only
  based on ht->slot.
sql/sql_cursor.cc:
  Update to the new layout of thd->transaction.
sql/sql_delete.cc:
  Remove wrong and now redundant calls to ha_autocommit_or_rollback.
  The transaction is committed in one place, at the end of the statement.
  Remove calls to mysql_unlock_tables, since some engines count locks
  and commit statement transaction in unlock_tables(), which essentially
  equates mysql_unlock_tables to ha_autocommit_or_rollback.
  Previously it was necessary to unlock tables soon because we wanted
  to avoid sending of 'ok' packet to the client under locked tables.
  This is no longer necessary, since OK packet is also sent from one place
  at the end of transaction.
sql/sql_do.cc:
  Add DO always clears the error, we must rollback the current
  statement before this happens. Otherwise the statement will be committed,
  and not rolled back in the end.
sql/sql_insert.cc:
  Remove wrong and now redundant calls to ha_autocommit_or_rollback.
  The transaction is committed in one place, at the end of the statement.
  Remove calls to mysql_unlock_tables, since some engines count locks
  and commit statement transaction in unlock_tables(), which essentially
  equates mysql_unlock_tables to ha_autocommit_or_rollback.
  Previously it was necessary to unlock tables soon because we wanted
  to avoid sending of 'ok' packet to the client under locked tables.
  This is no longer necessary, since OK packet is also sent from one place
  at the end of transaction.
sql/sql_load.cc:
  Remove wrong and now redundant calls to ha_autocommit_or_rollback.
  The transaction is committed in one place, at the end of the statement.
  Remove calls to mysql_unlock_tables, since some engines count locks
  and commit statement transaction in unlock_tables(), which essentially
  equates mysql_unlock_tables to ha_autocommit_or_rollback.
  Previously it was necessary to unlock tables soon because we wanted
  to avoid sending of 'ok' packet to the client under locked tables.
  This is no longer necessary, since OK packet is also sent from one place
  at the end of transaction.
sql/sql_parse.cc:
  Implement optimisation of read-only transactions: bypass 2-phase
  commit for them.
  Always commit statement transaction before commiting the global one.
  Fix an unrelated crash in check_table_access, when called from 
  information_schema.
sql/sql_partition.cc:
  Partitions commit at the end of a DDL operation.
  Make sure that send_ok() is done only if the commit has succeeded.
sql/sql_table.cc:
  Use ha_autocommit_or_rollback and end_active_trans everywhere.
  Add end_trans to mysql_admin_table, so that it leaves no pending
  transaction.
sql/sql_udf.cc:
  Remvove a redundant call to close_thread_tables()
sql/sql_update.cc:
  Remove wrong and now redundant calls to ha_autocommit_or_rollback.
  The transaction is committed in one place, at the end of the statement.
  Remove calls to mysql_unlock_tables, since some engines count locks
  and commit statement transaction in unlock_tables(), which essentially
  equates mysql_unlock_tables to ha_autocommit_or_rollback.
  Previously it was necessary to unlock tables soon because we wanted
  to avoid sending of 'ok' packet to the client under locked tables.
  This is no longer necessary, since OK packet is also sent from one place
  at the end of transaction.
mysql-test/include/commit.inc:
  New BitKeeper file ``mysql-test/include/commit.inc''
mysql-test/r/commit_1innodb.result:
  New BitKeeper file ``mysql-test/r/commit_1innodb.result''
mysql-test/t/commit_1innodb.test:
  New BitKeeper file ``mysql-test/t/commit_1innodb.test''