* Add state destroy to SHA2 API
* Include optimized SPHINCS+ implementations
I've generated new implementations from the sphincsplus repository.
* Don't destroy sha256ctx after finalize
* Attempt to shut up MSVC
* Make sure to drop errors in rmtree
* Names passed around (mostly constant) value more clearly
* Put ``const`` where applicable (almost everywhere)
* Renamed ``primitive.h``
* Fixed some nits