MINOR: protocol: rename the ->listeners field to ->receivers

Since the listeners were split into receiver+listener, this field ought
to have been renamed because it's confusing. It really links receivers
and not listeners, as most of the time it's used via rx.proto_list!
The nb_listeners field was updated accordingly.
diff --git a/src/protocol.c b/src/protocol.c
index c9d2675..c0a0090 100644
--- a/src/protocol.c
+++ b/src/protocol.c
@@ -71,7 +71,7 @@
 	err = 0;
 	HA_SPIN_LOCK(PROTO_LOCK, &proto_lock);
 	list_for_each_entry(proto, &protocols, list) {
-		list_for_each_entry(receiver, &proto->listeners, proto_list) {
+		list_for_each_entry(receiver, &proto->receivers, proto_list) {
 			listener = LIST_ELEM(receiver, struct listener *, rx);
 
 			/* FIXME: horrible hack, we don't have a way to register
@@ -144,7 +144,7 @@
 	err = 0;
 	HA_SPIN_LOCK(PROTO_LOCK, &proto_lock);
 	list_for_each_entry(proto, &protocols, list) {
-		list_for_each_entry(listener, &proto->listeners, rx.proto_list)
+		list_for_each_entry(listener, &proto->receivers, rx.proto_list)
 			unbind_listener(listener);
 	}
 	HA_SPIN_UNLOCK(PROTO_LOCK, &proto_lock);
@@ -165,7 +165,7 @@
 	err = 0;
 	HA_SPIN_LOCK(PROTO_LOCK, &proto_lock);
 	list_for_each_entry(proto, &protocols, list) {
-		list_for_each_entry(listener, &proto->listeners, rx.proto_list)
+		list_for_each_entry(listener, &proto->receivers, rx.proto_list)
 			if (!pause_listener(listener))
 				err |= ERR_FATAL;
 	}
@@ -187,7 +187,7 @@
 	err = 0;
 	HA_SPIN_LOCK(PROTO_LOCK, &proto_lock);
 	list_for_each_entry(proto, &protocols, list) {
-		list_for_each_entry(listener, &proto->listeners, rx.proto_list)
+		list_for_each_entry(listener, &proto->receivers, rx.proto_list)
 			if (!resume_listener(listener))
 				err |= ERR_FATAL;
 	}
@@ -206,7 +206,7 @@
 
 	HA_SPIN_LOCK(PROTO_LOCK, &proto_lock);
 	list_for_each_entry(proto, &protocols, list) {
-		list_for_each_entry(listener, &proto->listeners, rx.proto_list)
+		list_for_each_entry(listener, &proto->receivers, rx.proto_list)
 			enable_listener(listener);
 	}
 	HA_SPIN_UNLOCK(PROTO_LOCK, &proto_lock);