update against upstream

[redshiftzero]

The task here is to update these bindings for upstream changes. This can be done a few commits at a time to make it easier to review.

The process here is:

1. Update commits (if needed) in our fork compared to upstream
2. Update the relevant bindings in this repository
3. Update the rev we build against in: https://github.com/freedomofpress/signal-protocol/blob/main/Cargo.toml#L10

[redshiftzero]

https://github.com/freedomofpress/signal-protocol/commit/8fc826a3289d106a5f77771073819f6cfb2f0fbd is an example of how to update vs the upstream project