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 lets you block connections to remote servers at the s2s
level.

``` {.lua}
s2s_blacklist = {
    "proxy.eu.jabber.org",
}
```