change test framework to use files for in and out (s-exp)

test/cases/compound/array_ops.tst

@@ -0,0 +1,8 @@
+[ 3 + 4 , foo(22) ]
+-- -- --
+s(:list,  [s(:array,  [s(:operator,  "+", 
+  s(:int,  3), 
+  s(:int,  4)), s(:call, 
+  s(:name,  "foo"), 
+  s(:arguments, 
+    s(:int,  22)))])])