guile: Add bindings for 'gnutls_server_name_set'.

This adds the 'set-session-server-name!' procedure and the
'server-name-type' enum type.
guile: Restore cross-reference in 'set-session-priorities!' docstring.

This had been destroyed in 32d90395.
only enable crywrap if libidn is present
removed gnutls_pcert_get_type()
more files to ignore
doc update
Add a function to obtain the trust list of a gnutls_certificate_credentials_t

Signed-off-by: Armin Burgmeier <armin@arbur.net>
Add functions to export X.509 and OpenPGP private keys from the abstract type

Signed-off-by: Armin Burgmeier <armin@arbur.net>
enabled gnutls_privkey_export_pkcs11
Add functions to obtain X.509 keys and certificates from certificate credentials

Signed-off-by: Armin Burgmeier <armin@arbur.net>
Add getter functions for openpgp keys and certificates

Signed-off-by: Armin Burgmeier <armin@arbur.net>
Add an interface to iterate the trusted CA certificates in a trust list

Signed-off-by: Armin Burgmeier <armin@arbur.net>
Check the credentials getter functions as part of the unit tests
enable gcc warnings by default
use unsigned types in prototypes
doc update