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/readonly2.right b/shell/hush_test/hush-vars/readonly2.right
new file mode 100644
index 0000000..5b02ddf
--- /dev/null
+++ b/shell/hush_test/hush-vars/readonly2.right
@@ -0,0 +1,4 @@
+hush: a=Z: readonly variable
+Visible:42
+hush: a=Z: readonly variable
+Visible:42