I just spent the last hour or so tracking down a couple of mysterious
'ht is already destroyed' messages.
It turns out that this is caused by zend_clean_module_rsrc_dtors_cb()
attempting to apply a callback function to the regular and persistent
lists. At the time this is called, those lists have already been
destroyed.
The attached patch is something of a hack to avoid bailing out in this
case. There might be a better way to handle this.
The problem only occurs with dl()'d modules that register resources.
