Version 0.10 adds support for user-defined window functions. ### Added - `FunctionImpl` has two new fields (`WindowValue` and `WindowInverse`) that allow creating [user-defined aggregate window functions][] ([#42](https://github.com/zombiezen/go-sqlite/issues/42)). [user-defined aggregate window functions]: https://www.sqlite.org/windowfunctions.html#user_defined_aggregate_window_functions ### Changed - The `AggregateStep` callback now returns an `error`.