Suricata

I recently ran into an issue where a plugin was using a sha256 library that had a function names sha256_transform. Suricata also has a function:

#[no_mangle]
extern "C" fn sha256_finalize

The plugin was using our version leading to a crash.

On our side we should:
- only use no_mangle for pub extern "C", and these must be prefixed with "SC"
- if not pub, we shouldn't need no_mangle, for example if the function is only ever used by pointer. We can let normal Rust mangling deal with it.

I plan to do this as a sweeping change.