Variant on Tree, try not to expand too much

tests/black/Test1.newt

@@ -1,9 +0,0 @@
-module Test1
-
-nat : U
-nat = {C : U} -> C -> (nat -> C) -> C
-
--- TESTCASE This was broken when I wasn't expanding Ref ty in check
--- Also broken when I tried to put Def in VRef
-succ : nat -> nat
-succ = \n => \ z s => s n