Improve use of GnuTLS in the gnutls-pkcs11 backend
Submitted by Michael Catanzaro
I want to split these tasks out of bug #753260, because I want to close that bug, but don't want to work on the PKCS#11 backend.
Make the PKCS#11 code use gnutls_x509_trust_list_t as well, using gnutls's built-in PKCS#11 support.
[Use] the trust list iterating API [gnutls_x509_trust_list_iter_get_ca] on the PKCS#11 side [to] get rid of most of our direct p11-kit use as well.