mod_sasl2, mod_sasl_bind2, mod_sasl2_sm: Bump XEP-0388 namespace This is the namespace for the proposed update to XEP-0388. I.e. not even experimental yet... but this is all a work in progress anyway.

This module blocks configured queries that change server state.

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

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