Exposes OpenSSL's PKCS5_PBKDF2_HMAC as a MySQL function. Currently this only uses SHA-512 with a key length of 64 bytes
To build + install on Ubuntu:
1. install `libmysqlclient-dev`, and `libssl-dev`
2. run `build.sh`
3. copy the resulting `libmysql-pbkdf2.so` to `/usr/lib/mysql/plugin`
4. Run `CREATE FUNCTION PBKDF2_SHA512 RETURNS STRING SONAME 'libmysql-pbkdf2.so'` in your db;