step 4: Test that (= (list) ()) is true

In APL, empty arrays have type, and the ≡ function pays attention to
that, so if you're not careful empty lists produced by different means
compare different.  This test detects that by comparing an empty list
produced by "list" with one produced by evaluating an empty list.

My bug was found by a deferrable step 4 test, but the bug should be
non-deferrable.

impls/tests/step4_if_fn_do.mal

@@ -119,6 +119,8 @@
 
 (= (list) (list))
 ;=>true
+(= (list) ())
+;=>true
 (= (list 1 2) (list 1 2))
 ;=>true
 (= (list 1) (list))