This one will be set by the transport layers which want to destroy
a bind_conf. It will typically be used by SSL to release certificates,
CAs and so on.
void (*close)(struct connection *); /* close the transport layer */
int (*init)(struct connection *conn); /* initialize the transport layer */
int (*prepare_bind_conf)(struct bind_conf *conf); /* prepare a whole bind_conf */
+ void (*destroy_bind_conf)(struct bind_conf *conf); /* destroy a whole bind_conf */
char name[8]; /* transport layer name, zero-terminated */
};