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

test/cases/module_def/module_assign_var.tst

@@ -0,0 +1,7 @@
+module Opers
+  abba = 5
+end
+-- -- --
+s(:list,  [s(:module,  "Opers",  [s(:assign, 
+  s(:name,  "abba"), 
+  s(:int,  5))])])