patch 7.4.1557
Problem:    Windows cannot be identified.
Solution:   Add a unique window number to each window and functions to use it.
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 5ad1718..233ca12 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -186,6 +186,7 @@
 	    test_viminfo.res \
 	    test_viml.res \
 	    test_visual.res \
+	    test_window_id.res \
 	    test_alot.res