Fix:
===
Backport Bug#11756194 to mysql-5.5. slave breaks if
'drop database' fails on master and mismatched tables on
slave.

'DROP TABLE <deleted tables>' was binlogged when
'DROP DATABASE' failed and at least one table was deleted
from the database. The log event would lead slave SQL thread
stop if some of the tables did not exist on slave.

After this patch, It is always binlogged with 'IF EXISTS'
option.