Add explicit test for recarray format descriptors
diff --git a/example/example20.ref b/example/example20.ref
index e69de29..6023a87 100644
--- a/example/example20.ref
+++ b/example/example20.ref
@@ -0,0 +1,3 @@
+T{?:x:xxxI:y:f:z:}
+T{?:x:=I:y:f:z:}
+T{T{?:x:xxxI:y:f:z:}:a:T{?:x:=I:y:f:z:}:b:}