Public key cryptography

Dear GnuTLS guilers,

This was a little harder than what I expected, but I now believe that I have most of the public key API that gnutls exports. Not everything is in there: notably, gost curves, some key generation flags, reproducible key generation, converting from and to openpgp keys. However, I believe this to be a good basis to implement the JWT algorithms for instance.

What do you think?

Best regards,

Vivien