hx509: Add hx509_ca_tbs_get_name()

This is so we can check if a TBS gets an empty subject name, then refuse
to issue the certificate if it doesn't also have at least one SAN.

lib/hx509/version-script.map

@@ -50,6 +50,7 @@ HEIMDAL_X509_1.2 {
 		hx509_ca_tbs_add_san_pkinit;
 		hx509_ca_tbs_add_san_rfc822name;
 		hx509_ca_tbs_free;
+		hx509_ca_tbs_get_name;
 		hx509_ca_tbs_init;
 		hx509_ca_tbs_set_ca;
 		hx509_ca_tbs_set_domaincontroller;