Store peer signature type.

Store peer signature type.

Store peer signature type in s->s3->tmp.peer_sigtype and check it
to see if the peer used PSS.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2301)