MINOR: connection: add a new prepare_bind_conf() entry to xprt_ops

This one will be set by the transport layers which want to initialize
a bind_conf. It will typically be used by SSL to load certificates, CAs
and so on.

include/types/connection.h

@@ -213,6 +213,7 @@ struct xprt_ops {
 	void (*shutw)(struct connection *, int);    /* shutw function */
 	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 */
 	char name[8];                               /* transport layer name, zero-terminated */
 };