py: Free unique_code slot for outer module.

Partly (very partly!) addresses issue #386.  Most importantly, at the
REPL command line, each invocation does not now lead to increased memory
usage (unless you define a function/lambda).
diff --git a/py/vm.c b/py/vm.c
index 60ed641..12cea7f 100644
--- a/py/vm.c
+++ b/py/vm.c
@@ -563,12 +563,12 @@
 
                     case MP_BC_MAKE_FUNCTION:
                         DECODE_UINT;
-                        PUSH(rt_make_function_from_id(unum, MP_OBJ_NULL));
+                        PUSH(rt_make_function_from_id(unum, false, MP_OBJ_NULL));
                         break;
 
                     case MP_BC_MAKE_FUNCTION_DEFARGS:
                         DECODE_UINT;
-                        SET_TOP(rt_make_function_from_id(unum, TOP()));
+                        SET_TOP(rt_make_function_from_id(unum, false, TOP()));
                         break;
 
                     case MP_BC_MAKE_CLOSURE: