As discussed in #802 it is pretty awkward that ToSql and FromSql are not implemented for u64. The current justification is that SQLite cannot actually store integers between i64::MAX and u64::MAX, but it would be simpler just to return an error in that case (FromSqlError::OutOfRange, or is it Error::IntegralValueOutOfRange, or possibly Error::FromSqlConversionFailure?).