mod_s2s_keepalive: Don't send whitespace keepalives before s2sin stream is open Could possibly result in whitespace before the XML and stream header, which isn't allowed by the parser. Don't think s2sout is affected, as the stream is opened early and doesn't have to wait for the other end. Thanks Ge0rG

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.