NON-EXISTS RECORDS

Problem:
========
In RBR replication, master deletes a record but the record
don't exist on slave. when slave tries to apply the
Delete_row_log_event from master, it will result in an
assert on slave.

Analysis:
========
This problem exists not only with Delete_rows event but also
with Update_rows event as well. Trying to update a non
existing row on the slave from the master will cause the
same assert.  This assert occurs only for the tables that
doesn't have primary keys and which basically require
sequential scan to be done to locate a record. This bug
occurs only with innodb engine not with myisam.

When update or delete rows is executed on a slave on a table
which doesn't have primary key the updated record is stored
in a buffer named table->record[0] and the same is copied to
table->record[1] so that during sequential scan
table->record[0] can reloaded with fetched data from the
table and compared against table->record[1].  In a special
case where there is no record on the slave side scan will
result in EOF in that case we reinit the scan and we try to
compare record[0]  with record[1] which are basically the
same. This comparison is incorrect. Since they both are the
same record_compare() will report that record is found and
we try to go ahead and try to update/delete non existing
row. Ideally if the scan results in EOF means no data found
hence no need to do a record_compare() at all.

Fix:
===
Avoid comparision of records on EOF.

sql/log_event.cc:
  Avoid record comparison on end of file.
sql/log_event_old.cc:
  Avoid record comparison on end of file.