updated for version 7.3.038
Problem:    v:windowid isn't set on MS-Windows.
Solution:   Set it to the window handle. (Chris Sutcliffe)
diff --git a/src/gui_w32.c b/src/gui_w32.c
index 5071423..f3b9c5b 100644
--- a/src/gui_w32.c
+++ b/src/gui_w32.c
@@ -1573,6 +1573,11 @@
 # endif
 #endif
 
+#ifdef FEAT_EVAL
+    /* set the v:windowid variable */
+    set_vim_var_nr(VV_WINDOWID, (long)s_hwnd);
+#endif
+
 theend:
     /* Display any pending error messages */
     display_errors();