Add getters for X509_STORE and X509_OBJECT members

OpenSSL 1.1.0-pre5 has made some additional structs opaque. Python's ssl
module requires access to some of the struct members. Three new getters
are added:

int X509_OBJECT_get_type(X509_OBJECT *a);
STACK_OF(X509_OBJECT) *X509_STORE_get0_objects(X509_STORE *v);
X509_VERIFY_PARAM *X509_STORE_get0_param(X509_STORE *ctx);

Signed-off-by: Christian Heimes <cheimes@redhat.com>

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>