affected_row_count should be implemented for all executed statements (including Prepared)

[jpastuszek]

Currently affected_row_count method is available for direct query (Allocated/Executed) and Prepared with HasResult but not for prepared query with NoResult.
If you run INSERT via prepared query you can't get the number of affected rows.

This looks all wrong to me though... Executed is an alias Allocated so you can't distinguish based on this on type system level. Also Prepared has no concept of Executed so you can only work with HasResult/NoResult on type system level. Ideally you could add another type parameter and have two pairs Direct/Prepared and Allocated/Executed so that you can implement affected_row_count to any type that is Executed and change Executed to Allocated with close_cursor method.