testcase for 67468 (only for debug build, as I could not create a stable segfault without loading other exts like pgsql)

Zend/tests/67468.phpt

@@ -0,0 +1,11 @@
+--TEST--
+Bug #67468 (Segfault in highlight_file()/highlight_string())
+--SKIPIF--
+<?php if(!function_exists("leak")) print "skip only for debug builds"; ?>
+--FILE--
+<?php
+highlight_string("<?php __CLASS__;", true);
+echo "done";
+?>
+--EXPECT--
+done