mod_pubsub_serverinfo: Consider sibling vhosts 'connected' Prosody does not have s2s connections between vhosts. Multiple domains will therefor not show up as each-other 'remote domains'. With this commit, the module considers vhosts permanently s2s-connected. Additional debug logging has been added.

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.