mod_cloud_notify: use stanza from mod_smacks to behave O(1) This uses the provided stanza in the ack-delayed smacks event to trigger push for this stanza only rather than iterating through the whole smacks queue to find the first unpushed stanza.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```