MINOR: obj_type: new object type for struct stream

This patch creates a new obj_type for the struct stream in HAProxy.
diff --git a/include/types/stream.h b/include/types/stream.h
index 93a39a3..b6a3e84 100644
--- a/include/types/stream.h
+++ b/include/types/stream.h
@@ -151,7 +151,9 @@
 		struct stktable *table;
 	} store[8];                     /* tracked stickiness values to store */
 	int store_count;
-	/* 4 unused bytes here */
+
+	enum obj_type obj_type;         /* object type == OBJ_TYPE_STREAM */
+	/* 3 unused bytes here */
 
 	struct stkctr stkctr[MAX_SESS_STKCTR];  /* content-aware stick counters */