mod_pubsub_serverinfo: Update to use mod_server_info (fixes #1841)
...but only for Prosody trunk users, because 0.12 mod_server_contact_info does
not use the new API in mod_server_info.
-- this module is deprecated, log an error and load the superseding module instead
module:depends"smacks"
module:log("error", "mod_smacks_offline is deprecated! Just use mod_smacks!");