Add sanity check against ze1_compatibility_mode.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

tests/HTMLPurifier/PHPT/ze1_compatibility_mode.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Error with zend.ze1_compatibility_mode test
+--PRESKIPIF--
+<?php
+if (version_compare(PHP_VERSION, '5.3.0') >= 0) {
+    echo 'skip - ze1_compatibility_mode not present in PHP 5.3 or later';
+}
+--INI--
+zend.ze1_compatibility_mode = 1
+--FILE--
+<?php
+require '../library/HTMLPurifier.auto.php';
+--EXPECTF--
+Fatal error: HTML Purifier is not compatible with zend.ze1_compatibility_mode; please turn it off in %s

tests/PHPT/Section/PRESKIPIF.php

@@ -0,0 +1,36 @@
+<?php
+
+class PHPT_Section_PRESKIPIF implements PHPT_Section_RunnableBefore
+{
+    private $_data = null;
+    private $_runner_factory = null;
+    
+    public function __construct($data)
+    {
+        $this->_data = $data;
+        $this->_runner_factory = new PHPT_CodeRunner_Factory();
+    }
+    
+    public function run(PHPT_Case $case)
+    {
+        // @todo refactor this code into PHPT_Util class as its used in multiple places
+        $filename = dirname($case->filename) . '/' . basename($case->filename, '.php') . '.skip.php';
+        
+        // @todo refactor to PHPT_CodeRunner
+        file_put_contents($filename, $this->_data);
+        $runner = $this->_runner_factory->factory($case);
+        $runner->ini = "";
+        $response = $runner->run($filename)->output;
+        unlink($filename);
+        
+        if (preg_match('/^skip( - (.*))?/', $response, $matches)) {
+            $message = !empty($matches[2]) ? $matches[2] : '';
+            throw new PHPT_Case_VetoException($message);
+        }
+    }
+    
+    public function getPriority()
+    {
+        return -2;
+    }
+}