after rollback on master

When starting a transaction with a statement containing changes
to both transactional tables and non-transactional tables, the
statement is considered as non-transactional and is therefore
written directly to the binary log. This behaviour was present
in 5.0, and has propagated to 5.1.

If a trigger containing a change of a non-transactional table is
added to a transactional table, any changes to the transactional
table is "tainted" as non-transactional.

This patch solves the problem by removing the existing "hack" that
allows non-transactional statements appearing first in a transaction
to be written directly to the binary log. Instead, anything inside
a transaction is treaded as part of the transaction and not written
to the binary log until the transaction is committed.