MINOR: connection: add a field to store an object type

This will soon be used to differenciate connections from applet
contexts. Object type "connection" has also been added.
diff --git a/include/types/obj_type.h b/include/types/obj_type.h
index b27f375..88d8973 100644
--- a/include/types/obj_type.h
+++ b/include/types/obj_type.h
@@ -37,6 +37,7 @@
 	OBJ_TYPE_PROXY,        /* object is a struct proxy */
 	OBJ_TYPE_SERVER,       /* object is a struct server */
 	OBJ_TYPE_APPLET,       /* object is a struct si_applet */
+	OBJ_TYPE_CONN,         /* object is a struct connection */
 	OBJ_TYPE_ENTRIES       /* last one : number of entries */
 };