JustSCRAM

Who needs a full SASL implementation when you just want SCRAM?

Cryptographic functions are borrowed from the OpenBSD and LibreSSL projects.
Base64 is from hostapd / wpa_supplicant

https://tools.ietf.org/html/rfc5802
https://github.com/libressl-portable/portable
https://github.com/openbsd/src


Still left TODO:

* Switch salted password to base64 encoded in API
* Channel binding
* SASLprep
* Test result of every malloc (and asprintf)
* Fail all the places we should
* SHA-256 support https://tools.ietf.org/html/rfc7677
* Reorganize SHA-256 and SHA-512 into sha2/ directory
* Use libbsd instead of maintaining our own https://libbsd.freedesktop.org/
* Validate null termination of base64 decoder
* Support varying lengths of nonce