MINOR: listener: add a new "options" entry in bind_conf

There is no way to store useful info there, yet there's about one entry
per boolean. Let's add an "options" attribute which will collect various
options.

In practice, even the BC_O_SSL_* flags and a few info such as strict_sni
could move there.
diff --git a/include/haproxy/listener-t.h b/include/haproxy/listener-t.h
index 3f0ea58..f22f3b2 100644
--- a/include/haproxy/listener-t.h
+++ b/include/haproxy/listener-t.h
@@ -176,6 +176,7 @@
 	struct proxy *frontend;    /* the frontend all these listeners belong to, or NULL */
 	const struct mux_proto_list *mux_proto; /* the mux to use for all incoming connections (specified by the "proto" keyword) */
 	struct xprt_ops *xprt;     /* transport-layer operations for all listeners */
+	uint options;              /* set of BC_O_* flags */
 	int is_ssl;                /* SSL is required for these listeners */
 	int generate_certs;        /* 1 if generate-certificates option is set, else 0 */
 	int level;                 /* stats access level (ACCESS_LVL_*) */