Remove support for the "rijndael256-cbc", "rijndael192-cbc", and

"rijndael128-cbc" names for AES.  These are in the IANA namespace, but
never appeared in any secsh-transport draft, and no version of OpenSSH
has supported them without also supporting the aes*-cbc names.

"rijndael-cbc@lysator.liu.se" gets to live because it's in the private
namespace.

git-svn-id: svn://svn.tartarus.org/sgt/putty@5607 cda61777-01e9-0310-a592-d414129be87e