Use 'mysqltest' as test database instead of test_$1 or test1,test2 to not accidently delete an important database
Safety fix for mailformed MERGE files
binlog even if they changed nothing, and a test for this.
This is useful when users use these commands to clean up their master and slave by issuing
one command on master (assume master and slave have slightly different data for some
reason and you want to clean up both).
Note that I have not changed multi-table DELETE and multi-table UPDATE because their
error-reporting mechanism is more complicated.
