Bug #6559 DROP DATABASE forgets to drop triggers

Description:
When you create a trigger, it creates a .TRG file
in the database directory.  But DROP DATABASE
doesn't know that it should drop the .TRG file,
and fails.

How to repeat:
use test;
create table t (i int);
create trigger mytrig before insert on t for each row set @a = 1;
drop database test;

Result:

ERROR 1010 (HY000): Error dropping database (can't rmdir './test/', errno: 17)

Fixed in 5.0.4

Noted in 5.0.4 changelog.