I'm working on implementing user-defined virtual tables in my package ([zombiezen/go-sqlite#15](https://github.com/zombiezen/go-sqlite/issues/15)). In order to implement the `xBestIndex` callback, I need access to the `sqlite3_index_constraint`, `sqlite3_index_orderby`, and `sqlite3_index_constraint_usage` structs, which are present in `modernc.org/sqlite/lib`, but not exported. IIUC it's because they declared inline but not `typedef`'d. I'm not sure the best way to do this with the `modernc.org` compiler, else I would send this as a PR. Thanks as always!