Update to SQLite 3.8.1 (Issue #33)

Per our conversation in issue #33, here's a pull request that updates the bundled SQLite3 code to version 3.8.1. The tests pass and everything looks good on this end.

I deliberately separated the actual update from the dance required to revert and reapply the "Apply stat64 hack" commit, but let me know if you'd prefer this to be flattened.