I'm trying to reimplement a subset of SQLx's compile-time query type validation on top of rusqlite. The types were fairly easy as I could use the Statement::columns method, but AFAIK there's currently no way to get the nullability of columns.

It would be possible to do this with the raw ffi api through the sqlite3_column_origin_name and sqlite_column_origin_table calls combined with a pragma_table_info, as mentioned in #494 (comment), but there's no way to get a *mut sqlite3_stmt from a Statement on the main branch.

Would you be open for a PR that adds the two methods to Statement?:

fn column_origin_table(&self, col: usize) -> Option<String>
fn column_origin_name(&self, col: usize) -> Option<String>

(Or alternatively, a handle() method to Statement would also work)