Skip test under preloading

In this case we produce additional warnings when preloading
evaluates constants. Possibly we shouldn't be evaluating expressions
with side-effects during preloading, but for now just skip this
test.

Author: nikic

Zend/tests/class_constant_inheritance_mutable_data.phpt

@@ -1,5 +1,9 @@
 --TEST--
 Class constant inheritance with mutable data
+--SKIPIF--
+<?php
+if (getenv('SKIP_PRELOAD')) die('skip preload produces additional warnings');
+?>
 --FILE--
 <?php