More tests for multi-table-update & timestamp handling


mysql-test/r/innodb.result:
  New multi-table-update tests
mysql-test/r/multi_update.result:
  New multi-table-update tests
mysql-test/r/type_timestamp.result:
  New timestamp tests
mysql-test/t/innodb.test:
  New multi-table-update tests
mysql-test/t/multi_update.test:
  New multi-table-update tests
mysql-test/t/type_timestamp.test:
  New timestamp tests
sql/sql_select.cc:
  Fixed bug in safe mode checking
sql/sql_update.cc:
  Fixed bug in autocommit in multi-table-update