AUTO_INC COLUMN ONLY ON SLAVE

In RBR, if the slave's table as one additional auto_inc column,
then, it will insert the value 0 instead of generating the next
auto_inc number.

We fix this by checking that if an auto_inc extra column exists,
when compared to column data of the row event, we explicitly set
it to NULL and flag the engine that a nulled auto_inc column will
be inserted.