updated and uploaded

[jeff-davis]

Hi,

I see that this has gone a while without update, and I put some work into getting this modernized on stable rust, and uploaded to crates.io.

If you are still interested, feel free to comment or contribute to my version of this project: https://github.com/jeff-davis/postgres-extension.rs

It's not in perfect shape yet, of course, still a lot of work to do.