Make iat_time, exp_time, auth_time an integer, not a float. The spec
does not explicitly forbit float times, but some clients don't accept
this (mod_auth_openidc), and `timetuple()` has second precision anyway
so we don't loose any information.
http://openid.net/specs/openid-connect-core-1_0.html#IDToken
If present in the Authentication Request, Authorization Servers MUST
include a nonce Claim in the ID Token with the Claim Value being the
nonce value sent in the Authentication Request.
This patch adds the nonce to the id_token.
