Inserting a negative value in the autoincrement column of a
partitioned innodb table was causing the value of the auto
increment counter to wrap around into a very large positive
value. The consequences are the same as if a very large positive
value was inserted into a column, e.g. reduced autoincrement
range, failure to read autoincrement counter.

The current patch ensures that before calculating the next
auto increment value, the current value is within the positive
maximum allowed limit.