BUG/MINOR: obj_type: Handle stream object in obj_base_ptr() function

The stream object (OBJ_TYPE_STREAM) was missing in the switch statement of the
obj_base_ptr() function.

This patch must be backported as far as 2.0.
diff --git a/include/proto/obj_type.h b/include/proto/obj_type.h
index c1ac5f4..799732b 100644
--- a/include/proto/obj_type.h
+++ b/include/proto/obj_type.h
@@ -198,6 +198,7 @@
 	case OBJ_TYPE_CONN:     return __objt_conn(t);
 	case OBJ_TYPE_SRVRQ:    return __objt_dns_srvrq(t);
 	case OBJ_TYPE_CS:       return __objt_cs(t);
+	case OBJ_TYPE_STREAM:   return __objt_stream(t);
 	case OBJ_TYPE_CHECK:    return __objt_check(t);
 	default:                return t; // exact pointer for invalid case
 	}