mod_pubsub_serverinfo: New module that uses pub/sub to make accessible server info This first implemetnation is laughably simple: it only adds a disco#info feature. This flags 'opt-in' for inclusion of local domain names in the data exposed by other domains (per the domain), which will allow servers to be listed in the XMPP Network Graph at https://xmppnetwork.goodbytes.im Hopefully, this bare-boned implementation acts as a stepping stone for future improvements.

This module logs events where more than a certain amount of CPU time was
spent.

``` lua
log_cpu_threshold = 0.01 -- in seconds, so this is 10 milliseconds
```

Uses the Lua
[`os.clock()`](http://www.lua.org/manual/5.2/manual.html#pdf-os.clock)
function to estimate CPU usage.