Because Rijndael is more known as AES, use crypto/aes instead of

crypto/rijndael.  Additionally, I applied the AES integration patch
from Stephen Sprunk <stephen@sprunk.org> and fiddled it to work
properly with the normal EVP constructs (and incidently work the same
way as all other symmetric cipher implementations).

This results in an API that looks a lot like the rest of the OpenSSL
cipher suite.