hush: another testcase for "READONLY_VAR=VAL BLTIN ..."

Currently fails.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/hush_test/hush-vars/readonly0.right b/shell/hush_test/hush-vars/readonly0.right
index 07ca6e0..8b750eb 100644
--- a/shell/hush_test/hush-vars/readonly0.right
+++ b/shell/hush_test/hush-vars/readonly0.right
@@ -1,14 +1,20 @@
 readonly a=A
 readonly b=B
 Ok:0
+
 hush: a=A: readonly variable
 Fail:1
 hush: a=A: readonly variable
 Fail:1
+
 hush: a=Z: readonly variable
 Fail:1
+
 hush: a=Z: readonly variable
 b=B
 ^^^a is not exported
+hush: a=Z: readonly variable
+Visible:42
+
 hush: a: readonly variable
 Fail:1